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Split C API docs in Py3k branch.

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@ -1,6 +1,5 @@
.. highlightlang:: c
.. _abstract:
**********************
@ -16,928 +15,11 @@ It is not possible to use these functions on objects that are not properly
initialized, such as a list object that has been created by :cfunc:`PyList_New`,
but whose items have not been set to some non-\ ``NULL`` value yet.
.. _object:
Object Protocol
===============
.. cfunction:: int PyObject_Print(PyObject *o, FILE *fp, int flags)
Print an object *o*, on file *fp*. Returns ``-1`` on error. The flags argument
is used to enable certain printing options. The only option currently supported
is :const:`Py_PRINT_RAW`; if given, the :func:`str` of the object is written
instead of the :func:`repr`.
.. cfunction:: int PyObject_HasAttr(PyObject *o, PyObject *attr_name)
Returns ``1`` if *o* has the attribute *attr_name*, and ``0`` otherwise. This
is equivalent to the Python expression ``hasattr(o, attr_name)``. This function
always succeeds.
.. cfunction:: int PyObject_HasAttrString(PyObject *o, const char *attr_name)
Returns ``1`` if *o* has the attribute *attr_name*, and ``0`` otherwise. This
is equivalent to the Python expression ``hasattr(o, attr_name)``. This function
always succeeds.
.. cfunction:: PyObject* PyObject_GetAttr(PyObject *o, PyObject *attr_name)
Retrieve an attribute named *attr_name* from object *o*. Returns the attribute
value on success, or *NULL* on failure. This is the equivalent of the Python
expression ``o.attr_name``.
.. cfunction:: PyObject* PyObject_GetAttrString(PyObject *o, const char *attr_name)
Retrieve an attribute named *attr_name* from object *o*. Returns the attribute
value on success, or *NULL* on failure. This is the equivalent of the Python
expression ``o.attr_name``.
.. cfunction:: int PyObject_SetAttr(PyObject *o, PyObject *attr_name, PyObject *v)
Set the value of the attribute named *attr_name*, for object *o*, to the value
*v*. Returns ``-1`` on failure. This is the equivalent of the Python statement
``o.attr_name = v``.
.. cfunction:: int PyObject_SetAttrString(PyObject *o, const char *attr_name, PyObject *v)
Set the value of the attribute named *attr_name*, for object *o*, to the value
*v*. Returns ``-1`` on failure. This is the equivalent of the Python statement
``o.attr_name = v``.
.. cfunction:: int PyObject_DelAttr(PyObject *o, PyObject *attr_name)
Delete attribute named *attr_name*, for object *o*. Returns ``-1`` on failure.
This is the equivalent of the Python statement ``del o.attr_name``.
.. cfunction:: int PyObject_DelAttrString(PyObject *o, const char *attr_name)
Delete attribute named *attr_name*, for object *o*. Returns ``-1`` on failure.
This is the equivalent of the Python statement ``del o.attr_name``.
.. cfunction:: PyObject* PyObject_RichCompare(PyObject *o1, PyObject *o2, int opid)
Compare the values of *o1* and *o2* using the operation specified by *opid*,
which must be one of :const:`Py_LT`, :const:`Py_LE`, :const:`Py_EQ`,
:const:`Py_NE`, :const:`Py_GT`, or :const:`Py_GE`, corresponding to ``<``,
``<=``, ``==``, ``!=``, ``>``, or ``>=`` respectively. This is the equivalent of
the Python expression ``o1 op o2``, where ``op`` is the operator corresponding
to *opid*. Returns the value of the comparison on success, or *NULL* on failure.
.. cfunction:: int PyObject_RichCompareBool(PyObject *o1, PyObject *o2, int opid)
Compare the values of *o1* and *o2* using the operation specified by *opid*,
which must be one of :const:`Py_LT`, :const:`Py_LE`, :const:`Py_EQ`,
:const:`Py_NE`, :const:`Py_GT`, or :const:`Py_GE`, corresponding to ``<``,
``<=``, ``==``, ``!=``, ``>``, or ``>=`` respectively. Returns ``-1`` on error,
``0`` if the result is false, ``1`` otherwise. This is the equivalent of the
Python expression ``o1 op o2``, where ``op`` is the operator corresponding to
*opid*.
.. cfunction:: int PyObject_Cmp(PyObject *o1, PyObject *o2, int *result)
.. index:: builtin: cmp
Compare the values of *o1* and *o2* using a routine provided by *o1*, if one
exists, otherwise with a routine provided by *o2*. The result of the comparison
is returned in *result*. Returns ``-1`` on failure. This is the equivalent of
the Python statement ``result = cmp(o1, o2)``.
.. cfunction:: int PyObject_Compare(PyObject *o1, PyObject *o2)
.. index:: builtin: cmp
Compare the values of *o1* and *o2* using a routine provided by *o1*, if one
exists, otherwise with a routine provided by *o2*. Returns the result of the
comparison on success. On error, the value returned is undefined; use
:cfunc:`PyErr_Occurred` to detect an error. This is equivalent to the Python
expression ``cmp(o1, o2)``.
.. cfunction:: PyObject* PyObject_Repr(PyObject *o)
.. index:: builtin: repr
Compute a string representation of object *o*. Returns the string
representation on success, *NULL* on failure. This is the equivalent of the
Python expression ``repr(o)``. Called by the :func:`repr` built-in function and
by reverse quotes.
.. cfunction:: PyObject* PyObject_Str(PyObject *o)
.. index:: builtin: str
Compute a string representation of object *o*. Returns the string
representation on success, *NULL* on failure. This is the equivalent of the
Python expression ``str(o)``. Called by the :func:`str` built-in function
and, therefore, by the :func:`print` function.
.. cfunction:: PyObject* PyObject_Unicode(PyObject *o)
.. index:: builtin: unicode
Compute a Unicode string representation of object *o*. Returns the Unicode
string representation on success, *NULL* on failure. This is the equivalent of
the Python expression ``unicode(o)``. Called by the :func:`unicode` built-in
function.
.. cfunction:: int PyObject_IsInstance(PyObject *inst, PyObject *cls)
Returns ``1`` if *inst* is an instance of the class *cls* or a subclass of
*cls*, or ``0`` if not. On error, returns ``-1`` and sets an exception. If
*cls* is a type object rather than a class object, :cfunc:`PyObject_IsInstance`
returns ``1`` if *inst* is of type *cls*. If *cls* is a tuple, the check will
be done against every entry in *cls*. The result will be ``1`` when at least one
of the checks returns ``1``, otherwise it will be ``0``. If *inst* is not a
class instance and *cls* is neither a type object, nor a class object, nor a
tuple, *inst* must have a :attr:`__class__` attribute --- the class relationship
of the value of that attribute with *cls* will be used to determine the result
of this function.
Subclass determination is done in a fairly straightforward way, but includes a
wrinkle that implementors of extensions to the class system may want to be aware
of. If :class:`A` and :class:`B` are class objects, :class:`B` is a subclass of
:class:`A` if it inherits from :class:`A` either directly or indirectly. If
either is not a class object, a more general mechanism is used to determine the
class relationship of the two objects. When testing if *B* is a subclass of
*A*, if *A* is *B*, :cfunc:`PyObject_IsSubclass` returns true. If *A* and *B*
are different objects, *B*'s :attr:`__bases__` attribute is searched in a
depth-first fashion for *A* --- the presence of the :attr:`__bases__` attribute
is considered sufficient for this determination.
.. cfunction:: int PyObject_IsSubclass(PyObject *derived, PyObject *cls)
Returns ``1`` if the class *derived* is identical to or derived from the class
*cls*, otherwise returns ``0``. In case of an error, returns ``-1``. If *cls*
is a tuple, the check will be done against every entry in *cls*. The result will
be ``1`` when at least one of the checks returns ``1``, otherwise it will be
``0``. If either *derived* or *cls* is not an actual class object (or tuple),
this function uses the generic algorithm described above.
.. cfunction:: int PyCallable_Check(PyObject *o)
Determine if the object *o* is callable. Return ``1`` if the object is callable
and ``0`` otherwise. This function always succeeds.
.. cfunction:: PyObject* PyObject_Call(PyObject *callable_object, PyObject *args, PyObject *kw)
Call a callable Python object *callable_object*, with arguments given by the
tuple *args*, and named arguments given by the dictionary *kw*. If no named
arguments are needed, *kw* may be *NULL*. *args* must not be *NULL*, use an
empty tuple if no arguments are needed. Returns the result of the call on
success, or *NULL* on failure. This is the equivalent of the Python expression
``callable_object(*args, **kw)``.
.. cfunction:: PyObject* PyObject_CallObject(PyObject *callable_object, PyObject *args)
Call a callable Python object *callable_object*, with arguments given by the
tuple *args*. If no arguments are needed, then *args* may be *NULL*. Returns
the result of the call on success, or *NULL* on failure. This is the equivalent
of the Python expression ``callable_object(*args)``.
.. cfunction:: PyObject* PyObject_CallFunction(PyObject *callable, char *format, ...)
Call a callable Python object *callable*, with a variable number of C arguments.
The C arguments are described using a :cfunc:`Py_BuildValue` style format
string. The format may be *NULL*, indicating that no arguments are provided.
Returns the result of the call on success, or *NULL* on failure. This is the
equivalent of the Python expression ``callable(*args)``. Note that if you only
pass :ctype:`PyObject \*` args, :cfunc:`PyObject_CallFunctionObjArgs` is a
faster alternative.
.. cfunction:: PyObject* PyObject_CallMethod(PyObject *o, char *method, char *format, ...)
Call the method named *method* of object *o* with a variable number of C
arguments. The C arguments are described by a :cfunc:`Py_BuildValue` format
string that should produce a tuple. The format may be *NULL*, indicating that
no arguments are provided. Returns the result of the call on success, or *NULL*
on failure. This is the equivalent of the Python expression ``o.method(args)``.
Note that if you only pass :ctype:`PyObject \*` args,
:cfunc:`PyObject_CallMethodObjArgs` is a faster alternative.
.. cfunction:: PyObject* PyObject_CallFunctionObjArgs(PyObject *callable, ..., NULL)
Call a callable Python object *callable*, with a variable number of
:ctype:`PyObject\*` arguments. The arguments are provided as a variable number
of parameters followed by *NULL*. Returns the result of the call on success, or
*NULL* on failure.
.. cfunction:: PyObject* PyObject_CallMethodObjArgs(PyObject *o, PyObject *name, ..., NULL)
Calls a method of the object *o*, where the name of the method is given as a
Python string object in *name*. It is called with a variable number of
:ctype:`PyObject\*` arguments. The arguments are provided as a variable number
of parameters followed by *NULL*. Returns the result of the call on success, or
*NULL* on failure.
.. cfunction:: long PyObject_Hash(PyObject *o)
.. index:: builtin: hash
Compute and return the hash value of an object *o*. On failure, return ``-1``.
This is the equivalent of the Python expression ``hash(o)``.
.. cfunction:: int PyObject_IsTrue(PyObject *o)
Returns ``1`` if the object *o* is considered to be true, and ``0`` otherwise.
This is equivalent to the Python expression ``not not o``. On failure, return
``-1``.
.. cfunction:: int PyObject_Not(PyObject *o)
Returns ``0`` if the object *o* is considered to be true, and ``1`` otherwise.
This is equivalent to the Python expression ``not o``. On failure, return
``-1``.
.. cfunction:: PyObject* PyObject_Type(PyObject *o)
.. index:: builtin: type
When *o* is non-*NULL*, returns a type object corresponding to the object type
of object *o*. On failure, raises :exc:`SystemError` and returns *NULL*. This
is equivalent to the Python expression ``type(o)``. This function increments the
reference count of the return value. There's really no reason to use this
function instead of the common expression ``o->ob_type``, which returns a
pointer of type :ctype:`PyTypeObject\*`, except when the incremented reference
count is needed.
.. cfunction:: int PyObject_TypeCheck(PyObject *o, PyTypeObject *type)
Return true if the object *o* is of type *type* or a subtype of *type*. Both
parameters must be non-*NULL*.
.. cfunction:: Py_ssize_t PyObject_Length(PyObject *o)
Py_ssize_t PyObject_Size(PyObject *o)
.. index:: builtin: len
Return the length of object *o*. If the object *o* provides either the sequence
and mapping protocols, the sequence length is returned. On error, ``-1`` is
returned. This is the equivalent to the Python expression ``len(o)``.
.. cfunction:: PyObject* PyObject_GetItem(PyObject *o, PyObject *key)
Return element of *o* corresponding to the object *key* or *NULL* on failure.
This is the equivalent of the Python expression ``o[key]``.
.. cfunction:: int PyObject_SetItem(PyObject *o, PyObject *key, PyObject *v)
Map the object *key* to the value *v*. Returns ``-1`` on failure. This is the
equivalent of the Python statement ``o[key] = v``.
.. cfunction:: int PyObject_DelItem(PyObject *o, PyObject *key)
Delete the mapping for *key* from *o*. Returns ``-1`` on failure. This is the
equivalent of the Python statement ``del o[key]``.
.. cfunction:: PyObject* PyObject_Dir(PyObject *o)
This is equivalent to the Python expression ``dir(o)``, returning a (possibly
empty) list of strings appropriate for the object argument, or *NULL* if there
was an error. If the argument is *NULL*, this is like the Python ``dir()``,
returning the names of the current locals; in this case, if no execution frame
is active then *NULL* is returned but :cfunc:`PyErr_Occurred` will return false.
.. cfunction:: PyObject* PyObject_GetIter(PyObject *o)
This is equivalent to the Python expression ``iter(o)``. It returns a new
iterator for the object argument, or the object itself if the object is already
an iterator. Raises :exc:`TypeError` and returns *NULL* if the object cannot be
iterated.
.. _number:
Number Protocol
===============
.. cfunction:: int PyNumber_Check(PyObject *o)
Returns ``1`` if the object *o* provides numeric protocols, and false otherwise.
This function always succeeds.
.. cfunction:: PyObject* PyNumber_Add(PyObject *o1, PyObject *o2)
Returns the result of adding *o1* and *o2*, or *NULL* on failure. This is the
equivalent of the Python expression ``o1 + o2``.
.. cfunction:: PyObject* PyNumber_Subtract(PyObject *o1, PyObject *o2)
Returns the result of subtracting *o2* from *o1*, or *NULL* on failure. This is
the equivalent of the Python expression ``o1 - o2``.
.. cfunction:: PyObject* PyNumber_Multiply(PyObject *o1, PyObject *o2)
Returns the result of multiplying *o1* and *o2*, or *NULL* on failure. This is
the equivalent of the Python expression ``o1 * o2``.
.. cfunction:: PyObject* PyNumber_Divide(PyObject *o1, PyObject *o2)
Returns the result of dividing *o1* by *o2*, or *NULL* on failure. This is the
equivalent of the Python expression ``o1 / o2``.
.. cfunction:: PyObject* PyNumber_FloorDivide(PyObject *o1, PyObject *o2)
Return the floor of *o1* divided by *o2*, or *NULL* on failure. This is
equivalent to the "classic" division of integers.
.. cfunction:: PyObject* PyNumber_TrueDivide(PyObject *o1, PyObject *o2)
Return a reasonable approximation for the mathematical value of *o1* divided by
*o2*, or *NULL* on failure. The return value is "approximate" because binary
floating point numbers are approximate; it is not possible to represent all real
numbers in base two. This function can return a floating point value when
passed two integers.
.. cfunction:: PyObject* PyNumber_Remainder(PyObject *o1, PyObject *o2)
Returns the remainder of dividing *o1* by *o2*, or *NULL* on failure. This is
the equivalent of the Python expression ``o1 % o2``.
.. cfunction:: PyObject* PyNumber_Divmod(PyObject *o1, PyObject *o2)
.. index:: builtin: divmod
See the built-in function :func:`divmod`. Returns *NULL* on failure. This is
the equivalent of the Python expression ``divmod(o1, o2)``.
.. cfunction:: PyObject* PyNumber_Power(PyObject *o1, PyObject *o2, PyObject *o3)
.. index:: builtin: pow
See the built-in function :func:`pow`. Returns *NULL* on failure. This is the
equivalent of the Python expression ``pow(o1, o2, o3)``, where *o3* is optional.
If *o3* is to be ignored, pass :cdata:`Py_None` in its place (passing *NULL* for
*o3* would cause an illegal memory access).
.. cfunction:: PyObject* PyNumber_Negative(PyObject *o)
Returns the negation of *o* on success, or *NULL* on failure. This is the
equivalent of the Python expression ``-o``.
.. cfunction:: PyObject* PyNumber_Positive(PyObject *o)
Returns *o* on success, or *NULL* on failure. This is the equivalent of the
Python expression ``+o``.
.. cfunction:: PyObject* PyNumber_Absolute(PyObject *o)
.. index:: builtin: abs
Returns the absolute value of *o*, or *NULL* on failure. This is the equivalent
of the Python expression ``abs(o)``.
.. cfunction:: PyObject* PyNumber_Invert(PyObject *o)
Returns the bitwise negation of *o* on success, or *NULL* on failure. This is
the equivalent of the Python expression ``~o``.
.. cfunction:: PyObject* PyNumber_Lshift(PyObject *o1, PyObject *o2)
Returns the result of left shifting *o1* by *o2* on success, or *NULL* on
failure. This is the equivalent of the Python expression ``o1 << o2``.
.. cfunction:: PyObject* PyNumber_Rshift(PyObject *o1, PyObject *o2)
Returns the result of right shifting *o1* by *o2* on success, or *NULL* on
failure. This is the equivalent of the Python expression ``o1 >> o2``.
.. cfunction:: PyObject* PyNumber_And(PyObject *o1, PyObject *o2)
Returns the "bitwise and" of *o1* and *o2* on success and *NULL* on failure.
This is the equivalent of the Python expression ``o1 & o2``.
.. cfunction:: PyObject* PyNumber_Xor(PyObject *o1, PyObject *o2)
Returns the "bitwise exclusive or" of *o1* by *o2* on success, or *NULL* on
failure. This is the equivalent of the Python expression ``o1 ^ o2``.
.. cfunction:: PyObject* PyNumber_Or(PyObject *o1, PyObject *o2)
Returns the "bitwise or" of *o1* and *o2* on success, or *NULL* on failure.
This is the equivalent of the Python expression ``o1 | o2``.
.. cfunction:: PyObject* PyNumber_InPlaceAdd(PyObject *o1, PyObject *o2)
Returns the result of adding *o1* and *o2*, or *NULL* on failure. The operation
is done *in-place* when *o1* supports it. This is the equivalent of the Python
statement ``o1 += o2``.
.. cfunction:: PyObject* PyNumber_InPlaceSubtract(PyObject *o1, PyObject *o2)
Returns the result of subtracting *o2* from *o1*, or *NULL* on failure. The
operation is done *in-place* when *o1* supports it. This is the equivalent of
the Python statement ``o1 -= o2``.
.. cfunction:: PyObject* PyNumber_InPlaceMultiply(PyObject *o1, PyObject *o2)
Returns the result of multiplying *o1* and *o2*, or *NULL* on failure. The
operation is done *in-place* when *o1* supports it. This is the equivalent of
the Python statement ``o1 *= o2``.
.. cfunction:: PyObject* PyNumber_InPlaceDivide(PyObject *o1, PyObject *o2)
Returns the result of dividing *o1* by *o2*, or *NULL* on failure. The
operation is done *in-place* when *o1* supports it. This is the equivalent of
the Python statement ``o1 /= o2``.
.. cfunction:: PyObject* PyNumber_InPlaceFloorDivide(PyObject *o1, PyObject *o2)
Returns the mathematical floor of dividing *o1* by *o2*, or *NULL* on failure.
The operation is done *in-place* when *o1* supports it. This is the equivalent
of the Python statement ``o1 //= o2``.
.. cfunction:: PyObject* PyNumber_InPlaceTrueDivide(PyObject *o1, PyObject *o2)
Return a reasonable approximation for the mathematical value of *o1* divided by
*o2*, or *NULL* on failure. The return value is "approximate" because binary
floating point numbers are approximate; it is not possible to represent all real
numbers in base two. This function can return a floating point value when
passed two integers. The operation is done *in-place* when *o1* supports it.
.. cfunction:: PyObject* PyNumber_InPlaceRemainder(PyObject *o1, PyObject *o2)
Returns the remainder of dividing *o1* by *o2*, or *NULL* on failure. The
operation is done *in-place* when *o1* supports it. This is the equivalent of
the Python statement ``o1 %= o2``.
.. cfunction:: PyObject* PyNumber_InPlacePower(PyObject *o1, PyObject *o2, PyObject *o3)
.. index:: builtin: pow
See the built-in function :func:`pow`. Returns *NULL* on failure. The operation
is done *in-place* when *o1* supports it. This is the equivalent of the Python
statement ``o1 **= o2`` when o3 is :cdata:`Py_None`, or an in-place variant of
``pow(o1, o2, o3)`` otherwise. If *o3* is to be ignored, pass :cdata:`Py_None`
in its place (passing *NULL* for *o3* would cause an illegal memory access).
.. cfunction:: PyObject* PyNumber_InPlaceLshift(PyObject *o1, PyObject *o2)
Returns the result of left shifting *o1* by *o2* on success, or *NULL* on
failure. The operation is done *in-place* when *o1* supports it. This is the
equivalent of the Python statement ``o1 <<= o2``.
.. cfunction:: PyObject* PyNumber_InPlaceRshift(PyObject *o1, PyObject *o2)
Returns the result of right shifting *o1* by *o2* on success, or *NULL* on
failure. The operation is done *in-place* when *o1* supports it. This is the
equivalent of the Python statement ``o1 >>= o2``.
.. cfunction:: PyObject* PyNumber_InPlaceAnd(PyObject *o1, PyObject *o2)
Returns the "bitwise and" of *o1* and *o2* on success and *NULL* on failure. The
operation is done *in-place* when *o1* supports it. This is the equivalent of
the Python statement ``o1 &= o2``.
.. cfunction:: PyObject* PyNumber_InPlaceXor(PyObject *o1, PyObject *o2)
Returns the "bitwise exclusive or" of *o1* by *o2* on success, or *NULL* on
failure. The operation is done *in-place* when *o1* supports it. This is the
equivalent of the Python statement ``o1 ^= o2``.
.. cfunction:: PyObject* PyNumber_InPlaceOr(PyObject *o1, PyObject *o2)
Returns the "bitwise or" of *o1* and *o2* on success, or *NULL* on failure. The
operation is done *in-place* when *o1* supports it. This is the equivalent of
the Python statement ``o1 |= o2``.
.. cfunction:: PyObject* PyNumber_Int(PyObject *o)
.. index:: builtin: int
Returns the *o* converted to an integer object on success, or *NULL* on failure.
If the argument is outside the integer range a long object will be returned
instead. This is the equivalent of the Python expression ``int(o)``.
.. cfunction:: PyObject* PyNumber_Long(PyObject *o)
.. index:: builtin: long
Returns the *o* converted to an integer object on success, or *NULL* on
failure. This is the equivalent of the Python expression ``long(o)``.
.. cfunction:: PyObject* PyNumber_Float(PyObject *o)
.. index:: builtin: float
Returns the *o* converted to a float object on success, or *NULL* on failure.
This is the equivalent of the Python expression ``float(o)``.
.. cfunction:: PyObject* PyNumber_Index(PyObject *o)
Returns the *o* converted to a Python int or long on success or *NULL* with a
TypeError exception raised on failure.
.. cfunction:: Py_ssize_t PyNumber_AsSsize_t(PyObject *o, PyObject *exc)
Returns *o* converted to a Py_ssize_t value if *o* can be interpreted as an
integer. If *o* can be converted to a Python int or long but the attempt to
convert to a Py_ssize_t value would raise an :exc:`OverflowError`, then the
*exc* argument is the type of exception that will be raised (usually
:exc:`IndexError` or :exc:`OverflowError`). If *exc* is *NULL*, then the
exception is cleared and the value is clipped to *PY_SSIZE_T_MIN* for a negative
integer or *PY_SSIZE_T_MAX* for a positive integer.
.. cfunction:: int PyIndex_Check(PyObject *o)
Returns True if *o* is an index integer (has the nb_index slot of the
tp_as_number structure filled in).
.. _sequence:
Sequence Protocol
=================
.. cfunction:: int PySequence_Check(PyObject *o)
Return ``1`` if the object provides sequence protocol, and ``0`` otherwise.
This function always succeeds.
.. cfunction:: Py_ssize_t PySequence_Size(PyObject *o)
.. index:: builtin: len
Returns the number of objects in sequence *o* on success, and ``-1`` on failure.
For objects that do not provide sequence protocol, this is equivalent to the
Python expression ``len(o)``.
.. cfunction:: Py_ssize_t PySequence_Length(PyObject *o)
Alternate name for :cfunc:`PySequence_Size`.
.. cfunction:: PyObject* PySequence_Concat(PyObject *o1, PyObject *o2)
Return the concatenation of *o1* and *o2* on success, and *NULL* on failure.
This is the equivalent of the Python expression ``o1 + o2``.
.. cfunction:: PyObject* PySequence_Repeat(PyObject *o, Py_ssize_t count)
Return the result of repeating sequence object *o* *count* times, or *NULL* on
failure. This is the equivalent of the Python expression ``o * count``.
.. cfunction:: PyObject* PySequence_InPlaceConcat(PyObject *o1, PyObject *o2)
Return the concatenation of *o1* and *o2* on success, and *NULL* on failure.
The operation is done *in-place* when *o1* supports it. This is the equivalent
of the Python expression ``o1 += o2``.
.. cfunction:: PyObject* PySequence_InPlaceRepeat(PyObject *o, Py_ssize_t count)
Return the result of repeating sequence object *o* *count* times, or *NULL* on
failure. The operation is done *in-place* when *o* supports it. This is the
equivalent of the Python expression ``o *= count``.
.. cfunction:: PyObject* PySequence_GetItem(PyObject *o, Py_ssize_t i)
Return the *i*th element of *o*, or *NULL* on failure. This is the equivalent of
the Python expression ``o[i]``.
.. cfunction:: PyObject* PySequence_GetSlice(PyObject *o, Py_ssize_t i1, Py_ssize_t i2)
Return the slice of sequence object *o* between *i1* and *i2*, or *NULL* on
failure. This is the equivalent of the Python expression ``o[i1:i2]``.
.. cfunction:: int PySequence_SetItem(PyObject *o, Py_ssize_t i, PyObject *v)
Assign object *v* to the *i*th element of *o*. Returns ``-1`` on failure. This
is the equivalent of the Python statement ``o[i] = v``. This function *does
not* steal a reference to *v*.
.. cfunction:: int PySequence_DelItem(PyObject *o, Py_ssize_t i)
Delete the *i*th element of object *o*. Returns ``-1`` on failure. This is the
equivalent of the Python statement ``del o[i]``.
.. cfunction:: int PySequence_SetSlice(PyObject *o, Py_ssize_t i1, Py_ssize_t i2, PyObject *v)
Assign the sequence object *v* to the slice in sequence object *o* from *i1* to
*i2*. This is the equivalent of the Python statement ``o[i1:i2] = v``.
.. cfunction:: int PySequence_DelSlice(PyObject *o, Py_ssize_t i1, Py_ssize_t i2)
Delete the slice in sequence object *o* from *i1* to *i2*. Returns ``-1`` on
failure. This is the equivalent of the Python statement ``del o[i1:i2]``.
.. cfunction:: Py_ssize_t PySequence_Count(PyObject *o, PyObject *value)
Return the number of occurrences of *value* in *o*, that is, return the number
of keys for which ``o[key] == value``. On failure, return ``-1``. This is
equivalent to the Python expression ``o.count(value)``.
.. cfunction:: int PySequence_Contains(PyObject *o, PyObject *value)
Determine if *o* contains *value*. If an item in *o* is equal to *value*,
return ``1``, otherwise return ``0``. On error, return ``-1``. This is
equivalent to the Python expression ``value in o``.
.. cfunction:: Py_ssize_t PySequence_Index(PyObject *o, PyObject *value)
Return the first index *i* for which ``o[i] == value``. On error, return
``-1``. This is equivalent to the Python expression ``o.index(value)``.
.. cfunction:: PyObject* PySequence_List(PyObject *o)
Return a list object with the same contents as the arbitrary sequence *o*. The
returned list is guaranteed to be new.
.. cfunction:: PyObject* PySequence_Tuple(PyObject *o)
.. index:: builtin: tuple
Return a tuple object with the same contents as the arbitrary sequence *o* or
*NULL* on failure. If *o* is a tuple, a new reference will be returned,
otherwise a tuple will be constructed with the appropriate contents. This is
equivalent to the Python expression ``tuple(o)``.
.. cfunction:: PyObject* PySequence_Fast(PyObject *o, const char *m)
Returns the sequence *o* as a tuple, unless it is already a tuple or list, in
which case *o* is returned. Use :cfunc:`PySequence_Fast_GET_ITEM` to access the
members of the result. Returns *NULL* on failure. If the object is not a
sequence, raises :exc:`TypeError` with *m* as the message text.
.. cfunction:: PyObject* PySequence_Fast_GET_ITEM(PyObject *o, Py_ssize_t i)
Return the *i*th element of *o*, assuming that *o* was returned by
:cfunc:`PySequence_Fast`, *o* is not *NULL*, and that *i* is within bounds.
.. cfunction:: PyObject** PySequence_Fast_ITEMS(PyObject *o)
Return the underlying array of PyObject pointers. Assumes that *o* was returned
by :cfunc:`PySequence_Fast` and *o* is not *NULL*.
.. cfunction:: PyObject* PySequence_ITEM(PyObject *o, Py_ssize_t i)
Return the *i*th element of *o* or *NULL* on failure. Macro form of
:cfunc:`PySequence_GetItem` but without checking that
:cfunc:`PySequence_Check(o)` is true and without adjustment for negative
indices.
.. cfunction:: Py_ssize_t PySequence_Fast_GET_SIZE(PyObject *o)
Returns the length of *o*, assuming that *o* was returned by
:cfunc:`PySequence_Fast` and that *o* is not *NULL*. The size can also be
gotten by calling :cfunc:`PySequence_Size` on *o*, but
:cfunc:`PySequence_Fast_GET_SIZE` is faster because it can assume *o* is a list
or tuple.
.. _mapping:
Mapping Protocol
================
.. cfunction:: int PyMapping_Check(PyObject *o)
Return ``1`` if the object provides mapping protocol, and ``0`` otherwise. This
function always succeeds.
.. cfunction:: Py_ssize_t PyMapping_Length(PyObject *o)
.. index:: builtin: len
Returns the number of keys in object *o* on success, and ``-1`` on failure. For
objects that do not provide mapping protocol, this is equivalent to the Python
expression ``len(o)``.
.. cfunction:: int PyMapping_DelItemString(PyObject *o, char *key)
Remove the mapping for object *key* from the object *o*. Return ``-1`` on
failure. This is equivalent to the Python statement ``del o[key]``.
.. cfunction:: int PyMapping_DelItem(PyObject *o, PyObject *key)
Remove the mapping for object *key* from the object *o*. Return ``-1`` on
failure. This is equivalent to the Python statement ``del o[key]``.
.. cfunction:: int PyMapping_HasKeyString(PyObject *o, char *key)
On success, return ``1`` if the mapping object has the key *key* and ``0``
otherwise. This is equivalent to the Python expression ``key in o``.
This function always succeeds.
.. cfunction:: int PyMapping_HasKey(PyObject *o, PyObject *key)
Return ``1`` if the mapping object has the key *key* and ``0`` otherwise. This
is equivalent to the Python expression ``key in o``. This function always
succeeds.
.. cfunction:: PyObject* PyMapping_Keys(PyObject *o)
On success, return a list of the keys in object *o*. On failure, return *NULL*.
This is equivalent to the Python expression ``o.keys()``.
.. cfunction:: PyObject* PyMapping_Values(PyObject *o)
On success, return a list of the values in object *o*. On failure, return
*NULL*. This is equivalent to the Python expression ``o.values()``.
.. cfunction:: PyObject* PyMapping_Items(PyObject *o)
On success, return a list of the items in object *o*, where each item is a tuple
containing a key-value pair. On failure, return *NULL*. This is equivalent to
the Python expression ``o.items()``.
.. cfunction:: PyObject* PyMapping_GetItemString(PyObject *o, char *key)
Return element of *o* corresponding to the object *key* or *NULL* on failure.
This is the equivalent of the Python expression ``o[key]``.
.. cfunction:: int PyMapping_SetItemString(PyObject *o, char *key, PyObject *v)
Map the object *key* to the value *v* in object *o*. Returns ``-1`` on failure.
This is the equivalent of the Python statement ``o[key] = v``.
.. _iterator:
Iterator Protocol
=================
There are only a couple of functions specifically for working with iterators.
.. cfunction:: int PyIter_Check(PyObject *o)
Return true if the object *o* supports the iterator protocol.
.. cfunction:: PyObject* PyIter_Next(PyObject *o)
Return the next value from the iteration *o*. If the object is an iterator,
this retrieves the next value from the iteration, and returns *NULL* with no
exception set if there are no remaining items. If the object is not an
iterator, :exc:`TypeError` is raised, or if there is an error in retrieving the
item, returns *NULL* and passes along the exception.
To write a loop which iterates over an iterator, the C code should look
something like this::
PyObject *iterator = PyObject_GetIter(obj);
PyObject *item;
if (iterator == NULL) {
/* propagate error */
}
while (item = PyIter_Next(iterator)) {
/* do something with item */
...
/* release reference when done */
Py_DECREF(item);
}
Py_DECREF(iterator);
if (PyErr_Occurred()) {
/* propagate error */
}
else {
/* continue doing useful work */
}
.. _abstract-buffer:
Buffer Protocol
===============
.. cfunction:: int PyObject_AsCharBuffer(PyObject *obj, const char **buffer, Py_ssize_t *buffer_len)
Returns a pointer to a read-only memory location useable as character- based
input. The *obj* argument must support the single-segment character buffer
interface. On success, returns ``0``, sets *buffer* to the memory location and
*buffer_len* to the buffer length. Returns ``-1`` and sets a :exc:`TypeError`
on error.
.. cfunction:: int PyObject_AsReadBuffer(PyObject *obj, const void **buffer, Py_ssize_t *buffer_len)
Returns a pointer to a read-only memory location containing arbitrary data. The
*obj* argument must support the single-segment readable buffer interface. On
success, returns ``0``, sets *buffer* to the memory location and *buffer_len* to
the buffer length. Returns ``-1`` and sets a :exc:`TypeError` on error.
.. cfunction:: int PyObject_CheckReadBuffer(PyObject *o)
Returns ``1`` if *o* supports the single-segment readable buffer interface.
Otherwise returns ``0``.
.. cfunction:: int PyObject_AsWriteBuffer(PyObject *obj, void **buffer, Py_ssize_t *buffer_len)
Returns a pointer to a writable memory location. The *obj* argument must
support the single-segment, character buffer interface. On success, returns
``0``, sets *buffer* to the memory location and *buffer_len* to the buffer
length. Returns ``-1`` and sets a :exc:`TypeError` on error.
.. toctree::
object.rst
number.rst
sequence.rst
mapping.rst
iter.rst
objbuffer.rst

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.. highlightlang:: c
.. _allocating-objects:
Allocating Objects on the Heap
==============================
.. cfunction:: PyObject* _PyObject_New(PyTypeObject *type)
.. cfunction:: PyVarObject* _PyObject_NewVar(PyTypeObject *type, Py_ssize_t size)
.. cfunction:: PyObject* PyObject_Init(PyObject *op, PyTypeObject *type)
Initialize a newly-allocated object *op* with its type and initial reference.
Returns the initialized object. If *type* indicates that the object
participates in the cyclic garbage detector, it is added to the detector's set
of observed objects. Other fields of the object are not affected.
.. cfunction:: PyVarObject* PyObject_InitVar(PyVarObject *op, PyTypeObject *type, Py_ssize_t size)
This does everything :cfunc:`PyObject_Init` does, and also initializes the
length information for a variable-size object.
.. cfunction:: TYPE* PyObject_New(TYPE, PyTypeObject *type)
Allocate a new Python object using the C structure type *TYPE* and the Python
type object *type*. Fields not defined by the Python object header are not
initialized; the object's reference count will be one. The size of the memory
allocation is determined from the :attr:`tp_basicsize` field of the type object.
.. cfunction:: TYPE* PyObject_NewVar(TYPE, PyTypeObject *type, Py_ssize_t size)
Allocate a new Python object using the C structure type *TYPE* and the Python
type object *type*. Fields not defined by the Python object header are not
initialized. The allocated memory allows for the *TYPE* structure plus *size*
fields of the size given by the :attr:`tp_itemsize` field of *type*. This is
useful for implementing objects like tuples, which are able to determine their
size at construction time. Embedding the array of fields into the same
allocation decreases the number of allocations, improving the memory management
efficiency.
.. cfunction:: void PyObject_Del(PyObject *op)
Releases memory allocated to an object using :cfunc:`PyObject_New` or
:cfunc:`PyObject_NewVar`. This is normally called from the :attr:`tp_dealloc`
handler specified in the object's type. The fields of the object should not be
accessed after this call as the memory is no longer a valid Python object.
.. cfunction:: PyObject* Py_InitModule(char *name, PyMethodDef *methods)
Create a new module object based on a name and table of functions, returning
the new module object; the *methods* argument can be *NULL* if no methods are
to be defined for the module.
.. cfunction:: PyObject* Py_InitModule3(char *name, PyMethodDef *methods, char *doc)
Create a new module object based on a name and table of functions, returning
the new module object. The *methods* argument can be *NULL* if no methods
are to be defined for the module. If *doc* is non-*NULL*, it will be used to
define the docstring for the module.
.. cfunction:: PyObject* Py_InitModule4(char *name, PyMethodDef *methods, char *doc, PyObject *self, int apiver)
Create a new module object based on a name and table of functions, returning
the new module object. The *methods* argument can be *NULL* if no methods
are to be defined for the module. If *doc* is non-*NULL*, it will be used to
define the docstring for the module. If *self* is non-*NULL*, it will passed
to the functions of the module as their (otherwise *NULL*) first parameter.
(This was added as an experimental feature, and there are no known uses in
the current version of Python.) For *apiver*, the only value which should be
passed is defined by the constant :const:`PYTHON_API_VERSION`.
.. note::
Most uses of this function should probably be using the :cfunc:`Py_InitModule3`
instead; only use this if you are sure you need it.
.. cvar:: PyObject _Py_NoneStruct
Object which is visible in Python as ``None``. This should only be accessed
using the :cmacro:`Py_None` macro, which evaluates to a pointer to this
object.

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.. highlightlang:: c
.. _arg-parsing:
Parsing arguments and building values
=====================================
These functions are useful when creating your own extensions functions and
methods. Additional information and examples are available in
:ref:`extending-index`.
The first three of these functions described, :cfunc:`PyArg_ParseTuple`,
:cfunc:`PyArg_ParseTupleAndKeywords`, and :cfunc:`PyArg_Parse`, all use *format
strings* which are used to tell the function about the expected arguments. The
format strings use the same syntax for each of these functions.
A format string consists of zero or more "format units." A format unit
describes one Python object; it is usually a single character or a parenthesized
sequence of format units. With a few exceptions, a format unit that is not a
parenthesized sequence normally corresponds to a single address argument to
these functions. In the following description, the quoted form is the format
unit; the entry in (round) parentheses is the Python object type that matches
the format unit; and the entry in [square] brackets is the type of the C
variable(s) whose address should be passed.
``s`` (string or Unicode object) [const char \*]
Convert a Python string or Unicode object to a C pointer to a character string.
You must not provide storage for the string itself; a pointer to an existing
string is stored into the character pointer variable whose address you pass.
The C string is NUL-terminated. The Python string must not contain embedded NUL
bytes; if it does, a :exc:`TypeError` exception is raised. Unicode objects are
converted to C strings using the default encoding. If this conversion fails, a
:exc:`UnicodeError` is raised.
``s#`` (string, Unicode or any read buffer compatible object) [const char \*, int]
This variant on ``s`` stores into two C variables, the first one a pointer to a
character string, the second one its length. In this case the Python string may
contain embedded null bytes. Unicode objects pass back a pointer to the default
encoded string version of the object if such a conversion is possible. All
other read-buffer compatible objects pass back a reference to the raw internal
data representation.
``y`` (bytes object) [const char \*]
This variant on ``s`` convert a Python bytes object to a C pointer to a
character string. The bytes object must not contain embedded NUL bytes; if it
does, a :exc:`TypeError` exception is raised.
``y#`` (bytes object) [const char \*, int]
This variant on ``s#`` stores into two C variables, the first one a pointer to a
character string, the second one its length. This only accepts bytes objects.
``z`` (string or ``None``) [const char \*]
Like ``s``, but the Python object may also be ``None``, in which case the C
pointer is set to *NULL*.
``z#`` (string or ``None`` or any read buffer compatible object) [const char \*, int]
This is to ``s#`` as ``z`` is to ``s``.
``u`` (Unicode object) [Py_UNICODE \*]
Convert a Python Unicode object to a C pointer to a NUL-terminated buffer of
16-bit Unicode (UTF-16) data. As with ``s``, there is no need to provide
storage for the Unicode data buffer; a pointer to the existing Unicode data is
stored into the :ctype:`Py_UNICODE` pointer variable whose address you pass.
``u#`` (Unicode object) [Py_UNICODE \*, int]
This variant on ``u`` stores into two C variables, the first one a pointer to a
Unicode data buffer, the second one its length. Non-Unicode objects are handled
by interpreting their read-buffer pointer as pointer to a :ctype:`Py_UNICODE`
array.
``Z`` (Unicode or ``None``) [Py_UNICODE \*]
Like ``s``, but the Python object may also be ``None``, in which case the C
pointer is set to *NULL*.
``Z#`` (Unicode or ``None``) [Py_UNICODE \*, int]
This is to ``u#`` as ``Z`` is to ``u``.
``es`` (string, Unicode object or character buffer compatible object) [const char \*encoding, char \*\*buffer]
This variant on ``s`` is used for encoding Unicode and objects convertible to
Unicode into a character buffer. It only works for encoded data without embedded
NUL bytes.
This format requires two arguments. The first is only used as input, and
must be a :ctype:`const char\*` which points to the name of an encoding as a
NUL-terminated string, or *NULL*, in which case the default encoding is used.
An exception is raised if the named encoding is not known to Python. The
second argument must be a :ctype:`char\*\*`; the value of the pointer it
references will be set to a buffer with the contents of the argument text.
The text will be encoded in the encoding specified by the first argument.
:cfunc:`PyArg_ParseTuple` will allocate a buffer of the needed size, copy the
encoded data into this buffer and adjust *\*buffer* to reference the newly
allocated storage. The caller is responsible for calling :cfunc:`PyMem_Free` to
free the allocated buffer after use.
``et`` (string, Unicode object or character buffer compatible object) [const char \*encoding, char \*\*buffer]
Same as ``es`` except that 8-bit string objects are passed through without
recoding them. Instead, the implementation assumes that the string object uses
the encoding passed in as parameter.
``es#`` (string, Unicode object or character buffer compatible object) [const char \*encoding, char \*\*buffer, int \*buffer_length]
This variant on ``s#`` is used for encoding Unicode and objects convertible to
Unicode into a character buffer. Unlike the ``es`` format, this variant allows
input data which contains NUL characters.
It requires three arguments. The first is only used as input, and must be a
:ctype:`const char\*` which points to the name of an encoding as a
NUL-terminated string, or *NULL*, in which case the default encoding is used.
An exception is raised if the named encoding is not known to Python. The
second argument must be a :ctype:`char\*\*`; the value of the pointer it
references will be set to a buffer with the contents of the argument text.
The text will be encoded in the encoding specified by the first argument.
The third argument must be a pointer to an integer; the referenced integer
will be set to the number of bytes in the output buffer.
There are two modes of operation:
If *\*buffer* points a *NULL* pointer, the function will allocate a buffer of
the needed size, copy the encoded data into this buffer and set *\*buffer* to
reference the newly allocated storage. The caller is responsible for calling
:cfunc:`PyMem_Free` to free the allocated buffer after usage.
If *\*buffer* points to a non-*NULL* pointer (an already allocated buffer),
:cfunc:`PyArg_ParseTuple` will use this location as the buffer and interpret the
initial value of *\*buffer_length* as the buffer size. It will then copy the
encoded data into the buffer and NUL-terminate it. If the buffer is not large
enough, a :exc:`ValueError` will be set.
In both cases, *\*buffer_length* is set to the length of the encoded data
without the trailing NUL byte.
``et#`` (string, Unicode object or character buffer compatible object) [const char \*encoding, char \*\*buffer]
Same as ``es#`` except that string objects are passed through without recoding
them. Instead, the implementation assumes that the string object uses the
encoding passed in as parameter.
``b`` (integer) [char]
Convert a Python integer to a tiny int, stored in a C :ctype:`char`.
``B`` (integer) [unsigned char]
Convert a Python integer to a tiny int without overflow checking, stored in a C
:ctype:`unsigned char`.
``h`` (integer) [short int]
Convert a Python integer to a C :ctype:`short int`.
``H`` (integer) [unsigned short int]
Convert a Python integer to a C :ctype:`unsigned short int`, without overflow
checking.
``i`` (integer) [int]
Convert a Python integer to a plain C :ctype:`int`.
``I`` (integer) [unsigned int]
Convert a Python integer to a C :ctype:`unsigned int`, without overflow
checking.
``l`` (integer) [long int]
Convert a Python integer to a C :ctype:`long int`.
``k`` (integer) [unsigned long]
Convert a Python integer to a C :ctype:`unsigned long` without
overflow checking.
``L`` (integer) [PY_LONG_LONG]
Convert a Python integer to a C :ctype:`long long`. This format is only
available on platforms that support :ctype:`long long` (or :ctype:`_int64` on
Windows).
``K`` (integer) [unsigned PY_LONG_LONG]
Convert a Python integer to a C :ctype:`unsigned long long`
without overflow checking. This format is only available on platforms that
support :ctype:`unsigned long long` (or :ctype:`unsigned _int64` on Windows).
``n`` (integer) [Py_ssize_t]
Convert a Python integer to a C :ctype:`Py_ssize_t`.
``c`` (string of length 1) [char]
Convert a Python character, represented as a string of length 1, to a C
:ctype:`char`.
``f`` (float) [float]
Convert a Python floating point number to a C :ctype:`float`.
``d`` (float) [double]
Convert a Python floating point number to a C :ctype:`double`.
``D`` (complex) [Py_complex]
Convert a Python complex number to a C :ctype:`Py_complex` structure.
``O`` (object) [PyObject \*]
Store a Python object (without any conversion) in a C object pointer. The C
program thus receives the actual object that was passed. The object's reference
count is not increased. The pointer stored is not *NULL*.
``O!`` (object) [*typeobject*, PyObject \*]
Store a Python object in a C object pointer. This is similar to ``O``, but
takes two C arguments: the first is the address of a Python type object, the
second is the address of the C variable (of type :ctype:`PyObject\*`) into which
the object pointer is stored. If the Python object does not have the required
type, :exc:`TypeError` is raised.
``O&`` (object) [*converter*, *anything*]
Convert a Python object to a C variable through a *converter* function. This
takes two arguments: the first is a function, the second is the address of a C
variable (of arbitrary type), converted to :ctype:`void \*`. The *converter*
function in turn is called as follows::
status = converter(object, address);
where *object* is the Python object to be converted and *address* is the
:ctype:`void\*` argument that was passed to the :cfunc:`PyArg_Parse\*` function.
The returned *status* should be ``1`` for a successful conversion and ``0`` if
the conversion has failed. When the conversion fails, the *converter* function
should raise an exception.
``S`` (string) [PyStringObject \*]
Like ``O`` but requires that the Python object is a string object. Raises
:exc:`TypeError` if the object is not a string object. The C variable may also
be declared as :ctype:`PyObject\*`.
``U`` (Unicode string) [PyUnicodeObject \*]
Like ``O`` but requires that the Python object is a Unicode object. Raises
:exc:`TypeError` if the object is not a Unicode object. The C variable may also
be declared as :ctype:`PyObject\*`.
``t#`` (read-only character buffer) [char \*, int]
Like ``s#``, but accepts any object which implements the read-only buffer
interface. The :ctype:`char\*` variable is set to point to the first byte of
the buffer, and the :ctype:`int` is set to the length of the buffer. Only
single-segment buffer objects are accepted; :exc:`TypeError` is raised for all
others.
``w`` (read-write character buffer) [char \*]
Similar to ``s``, but accepts any object which implements the read-write buffer
interface. The caller must determine the length of the buffer by other means,
or use ``w#`` instead. Only single-segment buffer objects are accepted;
:exc:`TypeError` is raised for all others.
``w#`` (read-write character buffer) [char \*, int]
Like ``s#``, but accepts any object which implements the read-write buffer
interface. The :ctype:`char \*` variable is set to point to the first byte of
the buffer, and the :ctype:`int` is set to the length of the buffer. Only
single-segment buffer objects are accepted; :exc:`TypeError` is raised for all
others.
``(items)`` (tuple) [*matching-items*]
The object must be a Python sequence whose length is the number of format units
in *items*. The C arguments must correspond to the individual format units in
*items*. Format units for sequences may be nested.
It is possible to pass "long" integers (integers whose value exceeds the
platform's :const:`LONG_MAX`) however no proper range checking is done --- the
most significant bits are silently truncated when the receiving field is too
small to receive the value (actually, the semantics are inherited from downcasts
in C --- your mileage may vary).
A few other characters have a meaning in a format string. These may not occur
inside nested parentheses. They are:
``|``
Indicates that the remaining arguments in the Python argument list are optional.
The C variables corresponding to optional arguments should be initialized to
their default value --- when an optional argument is not specified,
:cfunc:`PyArg_ParseTuple` does not touch the contents of the corresponding C
variable(s).
``:``
The list of format units ends here; the string after the colon is used as the
function name in error messages (the "associated value" of the exception that
:cfunc:`PyArg_ParseTuple` raises).
``;``
The list of format units ends here; the string after the semicolon is used as
the error message *instead* of the default error message. Clearly, ``:`` and
``;`` mutually exclude each other.
Note that any Python object references which are provided to the caller are
*borrowed* references; do not decrement their reference count!
Additional arguments passed to these functions must be addresses of variables
whose type is determined by the format string; these are used to store values
from the input tuple. There are a few cases, as described in the list of format
units above, where these parameters are used as input values; they should match
what is specified for the corresponding format unit in that case.
For the conversion to succeed, the *arg* object must match the format and the
format must be exhausted. On success, the :cfunc:`PyArg_Parse\*` functions
return true, otherwise they return false and raise an appropriate exception.
.. cfunction:: int PyArg_ParseTuple(PyObject *args, const char *format, ...)
Parse the parameters of a function that takes only positional parameters into
local variables. Returns true on success; on failure, it returns false and
raises the appropriate exception.
.. cfunction:: int PyArg_VaParse(PyObject *args, const char *format, va_list vargs)
Identical to :cfunc:`PyArg_ParseTuple`, except that it accepts a va_list rather
than a variable number of arguments.
.. cfunction:: int PyArg_ParseTupleAndKeywords(PyObject *args, PyObject *kw, const char *format, char *keywords[], ...)
Parse the parameters of a function that takes both positional and keyword
parameters into local variables. Returns true on success; on failure, it
returns false and raises the appropriate exception.
.. cfunction:: int PyArg_VaParseTupleAndKeywords(PyObject *args, PyObject *kw, const char *format, char *keywords[], va_list vargs)
Identical to :cfunc:`PyArg_ParseTupleAndKeywords`, except that it accepts a
va_list rather than a variable number of arguments.
.. XXX deprecated, will be removed
.. cfunction:: int PyArg_Parse(PyObject *args, const char *format, ...)
Function used to deconstruct the argument lists of "old-style" functions ---
these are functions which use the :const:`METH_OLDARGS` parameter parsing
method. This is not recommended for use in parameter parsing in new code, and
most code in the standard interpreter has been modified to no longer use this
for that purpose. It does remain a convenient way to decompose other tuples,
however, and may continue to be used for that purpose.
.. cfunction:: int PyArg_UnpackTuple(PyObject *args, const char *name, Py_ssize_t min, Py_ssize_t max, ...)
A simpler form of parameter retrieval which does not use a format string to
specify the types of the arguments. Functions which use this method to retrieve
their parameters should be declared as :const:`METH_VARARGS` in function or
method tables. The tuple containing the actual parameters should be passed as
*args*; it must actually be a tuple. The length of the tuple must be at least
*min* and no more than *max*; *min* and *max* may be equal. Additional
arguments must be passed to the function, each of which should be a pointer to a
:ctype:`PyObject\*` variable; these will be filled in with the values from
*args*; they will contain borrowed references. The variables which correspond
to optional parameters not given by *args* will not be filled in; these should
be initialized by the caller. This function returns true on success and false if
*args* is not a tuple or contains the wrong number of elements; an exception
will be set if there was a failure.
This is an example of the use of this function, taken from the sources for the
:mod:`_weakref` helper module for weak references::
static PyObject *
weakref_ref(PyObject *self, PyObject *args)
{
PyObject *object;
PyObject *callback = NULL;
PyObject *result = NULL;
if (PyArg_UnpackTuple(args, "ref", 1, 2, &object, &callback)) {
result = PyWeakref_NewRef(object, callback);
}
return result;
}
The call to :cfunc:`PyArg_UnpackTuple` in this example is entirely equivalent to
this call to :cfunc:`PyArg_ParseTuple`::
PyArg_ParseTuple(args, "O|O:ref", &object, &callback)
.. cfunction:: PyObject* Py_BuildValue(const char *format, ...)
Create a new value based on a format string similar to those accepted by the
:cfunc:`PyArg_Parse\*` family of functions and a sequence of values. Returns
the value or *NULL* in the case of an error; an exception will be raised if
*NULL* is returned.
:cfunc:`Py_BuildValue` does not always build a tuple. It builds a tuple only if
its format string contains two or more format units. If the format string is
empty, it returns ``None``; if it contains exactly one format unit, it returns
whatever object is described by that format unit. To force it to return a tuple
of size 0 or one, parenthesize the format string.
When memory buffers are passed as parameters to supply data to build objects, as
for the ``s`` and ``s#`` formats, the required data is copied. Buffers provided
by the caller are never referenced by the objects created by
:cfunc:`Py_BuildValue`. In other words, if your code invokes :cfunc:`malloc`
and passes the allocated memory to :cfunc:`Py_BuildValue`, your code is
responsible for calling :cfunc:`free` for that memory once
:cfunc:`Py_BuildValue` returns.
In the following description, the quoted form is the format unit; the entry in
(round) parentheses is the Python object type that the format unit will return;
and the entry in [square] brackets is the type of the C value(s) to be passed.
The characters space, tab, colon and comma are ignored in format strings (but
not within format units such as ``s#``). This can be used to make long format
strings a tad more readable.
``s`` (string) [char \*]
Convert a null-terminated C string to a Python object. If the C string pointer
is *NULL*, ``None`` is used.
``s#`` (string) [char \*, int]
Convert a C string and its length to a Python object. If the C string pointer
is *NULL*, the length is ignored and ``None`` is returned.
``z`` (string or ``None``) [char \*]
Same as ``s``.
``z#`` (string or ``None``) [char \*, int]
Same as ``s#``.
``u`` (Unicode string) [Py_UNICODE \*]
Convert a null-terminated buffer of Unicode (UCS-2 or UCS-4) data to a Python
Unicode object. If the Unicode buffer pointer is *NULL*, ``None`` is returned.
``u#`` (Unicode string) [Py_UNICODE \*, int]
Convert a Unicode (UCS-2 or UCS-4) data buffer and its length to a Python
Unicode object. If the Unicode buffer pointer is *NULL*, the length is ignored
and ``None`` is returned.
``U`` (string) [char \*]
Convert a null-terminated C string to a Python unicode object. If the C string
pointer is *NULL*, ``None`` is used.
``U#`` (string) [char \*, int]
Convert a C string and its length to a Python unicode object. If the C string
pointer is *NULL*, the length is ignored and ``None`` is returned.
``i`` (integer) [int]
Convert a plain C :ctype:`int` to a Python integer object.
``b`` (integer) [char]
Convert a plain C :ctype:`char` to a Python integer object.
``h`` (integer) [short int]
Convert a plain C :ctype:`short int` to a Python integer object.
``l`` (integer) [long int]
Convert a C :ctype:`long int` to a Python integer object.
``B`` (integer) [unsigned char]
Convert a C :ctype:`unsigned char` to a Python integer object.
``H`` (integer) [unsigned short int]
Convert a C :ctype:`unsigned short int` to a Python integer object.
``I`` (integer/long) [unsigned int]
Convert a C :ctype:`unsigned int` to a Python long integer object.
``k`` (integer/long) [unsigned long]
Convert a C :ctype:`unsigned long` to a Python long integer object.
``L`` (long) [PY_LONG_LONG]
Convert a C :ctype:`long long` to a Python integer object. Only available
on platforms that support :ctype:`long long`.
``K`` (long) [unsigned PY_LONG_LONG]
Convert a C :ctype:`unsigned long long` to a Python integer object. Only
available on platforms that support :ctype:`unsigned long long`.
``n`` (int) [Py_ssize_t]
Convert a C :ctype:`Py_ssize_t` to a Python integer.
``c`` (string of length 1) [char]
Convert a C :ctype:`int` representing a character to a Python string of length
1.
``d`` (float) [double]
Convert a C :ctype:`double` to a Python floating point number.
``f`` (float) [float]
Same as ``d``.
``D`` (complex) [Py_complex \*]
Convert a C :ctype:`Py_complex` structure to a Python complex number.
``O`` (object) [PyObject \*]
Pass a Python object untouched (except for its reference count, which is
incremented by one). If the object passed in is a *NULL* pointer, it is assumed
that this was caused because the call producing the argument found an error and
set an exception. Therefore, :cfunc:`Py_BuildValue` will return *NULL* but won't
raise an exception. If no exception has been raised yet, :exc:`SystemError` is
set.
``S`` (object) [PyObject \*]
Same as ``O``.
``N`` (object) [PyObject \*]
Same as ``O``, except it doesn't increment the reference count on the object.
Useful when the object is created by a call to an object constructor in the
argument list.
``O&`` (object) [*converter*, *anything*]
Convert *anything* to a Python object through a *converter* function. The
function is called with *anything* (which should be compatible with :ctype:`void
\*`) as its argument and should return a "new" Python object, or *NULL* if an
error occurred.
``(items)`` (tuple) [*matching-items*]
Convert a sequence of C values to a Python tuple with the same number of items.
``[items]`` (list) [*matching-items*]
Convert a sequence of C values to a Python list with the same number of items.
``{items}`` (dictionary) [*matching-items*]
Convert a sequence of C values to a Python dictionary. Each pair of consecutive
C values adds one item to the dictionary, serving as key and value,
respectively.
If there is an error in the format string, the :exc:`SystemError` exception is
set and *NULL* returned.

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.. highlightlang:: c
.. _boolobjects:
Boolean Objects
---------------
Booleans in Python are implemented as a subclass of integers. There are only
two booleans, :const:`Py_False` and :const:`Py_True`. As such, the normal
creation and deletion functions don't apply to booleans. The following macros
are available, however.
.. cfunction:: int PyBool_Check(PyObject *o)
Return true if *o* is of type :cdata:`PyBool_Type`.
.. cvar:: PyObject* Py_False
The Python ``False`` object. This object has no methods. It needs to be
treated just like any other object with respect to reference counts.
.. cvar:: PyObject* Py_True
The Python ``True`` object. This object has no methods. It needs to be treated
just like any other object with respect to reference counts.
.. cmacro:: Py_RETURN_FALSE
Return :const:`Py_False` from a function, properly incrementing its reference
count.
.. cmacro:: Py_RETURN_TRUE
Return :const:`Py_True` from a function, properly incrementing its reference
count.
.. cfunction:: PyObject* PyBool_FromLong(long v)
Return a new reference to :const:`Py_True` or :const:`Py_False` depending on the
truth value of *v*.

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.. highlightlang:: c
.. _bufferobjects:
Buffer Objects
--------------
.. sectionauthor:: Greg Stein <gstein@lyra.org>
.. index::
object: buffer
single: buffer interface
Python objects implemented in C can export a group of functions called the
"buffer interface." These functions can be used by an object to expose its data
in a raw, byte-oriented format. Clients of the object can use the buffer
interface to access the object data directly, without needing to copy it first.
Two examples of objects that support the buffer interface are strings and
arrays. The string object exposes the character contents in the buffer
interface's byte-oriented form. An array can also expose its contents, but it
should be noted that array elements may be multi-byte values.
An example user of the buffer interface is the file object's :meth:`write`
method. Any object that can export a series of bytes through the buffer
interface can be written to a file. There are a number of format codes to
:cfunc:`PyArg_ParseTuple` that operate against an object's buffer interface,
returning data from the target object.
.. index:: single: PyBufferProcs
More information on the buffer interface is provided in the section
:ref:`buffer-structs`, under the description for :ctype:`PyBufferProcs`.
A "buffer object" is defined in the :file:`bufferobject.h` header (included by
:file:`Python.h`). These objects look very similar to string objects at the
Python programming level: they support slicing, indexing, concatenation, and
some other standard string operations. However, their data can come from one of
two sources: from a block of memory, or from another object which exports the
buffer interface.
Buffer objects are useful as a way to expose the data from another object's
buffer interface to the Python programmer. They can also be used as a zero-copy
slicing mechanism. Using their ability to reference a block of memory, it is
possible to expose any data to the Python programmer quite easily. The memory
could be a large, constant array in a C extension, it could be a raw block of
memory for manipulation before passing to an operating system library, or it
could be used to pass around structured data in its native, in-memory format.
.. ctype:: PyBufferObject
This subtype of :ctype:`PyObject` represents a buffer object.
.. cvar:: PyTypeObject PyBuffer_Type
.. index:: single: BufferType (in module types)
The instance of :ctype:`PyTypeObject` which represents the Python buffer type;
it is the same object as ``buffer`` and ``types.BufferType`` in the Python
layer. .
.. cvar:: int Py_END_OF_BUFFER
This constant may be passed as the *size* parameter to
:cfunc:`PyBuffer_FromObject` or :cfunc:`PyBuffer_FromReadWriteObject`. It
indicates that the new :ctype:`PyBufferObject` should refer to *base* object
from the specified *offset* to the end of its exported buffer. Using this
enables the caller to avoid querying the *base* object for its length.
.. cfunction:: int PyBuffer_Check(PyObject *p)
Return true if the argument has type :cdata:`PyBuffer_Type`.
.. cfunction:: PyObject* PyBuffer_FromObject(PyObject *base, Py_ssize_t offset, Py_ssize_t size)
Return a new read-only buffer object. This raises :exc:`TypeError` if *base*
doesn't support the read-only buffer protocol or doesn't provide exactly one
buffer segment, or it raises :exc:`ValueError` if *offset* is less than zero.
The buffer will hold a reference to the *base* object, and the buffer's contents
will refer to the *base* object's buffer interface, starting as position
*offset* and extending for *size* bytes. If *size* is :const:`Py_END_OF_BUFFER`,
then the new buffer's contents extend to the length of the *base* object's
exported buffer data.
.. cfunction:: PyObject* PyBuffer_FromReadWriteObject(PyObject *base, Py_ssize_t offset, Py_ssize_t size)
Return a new writable buffer object. Parameters and exceptions are similar to
those for :cfunc:`PyBuffer_FromObject`. If the *base* object does not export
the writable buffer protocol, then :exc:`TypeError` is raised.
.. cfunction:: PyObject* PyBuffer_FromMemory(void *ptr, Py_ssize_t size)
Return a new read-only buffer object that reads from a specified location in
memory, with a specified size. The caller is responsible for ensuring that the
memory buffer, passed in as *ptr*, is not deallocated while the returned buffer
object exists. Raises :exc:`ValueError` if *size* is less than zero. Note that
:const:`Py_END_OF_BUFFER` may *not* be passed for the *size* parameter;
:exc:`ValueError` will be raised in that case.
.. cfunction:: PyObject* PyBuffer_FromReadWriteMemory(void *ptr, Py_ssize_t size)
Similar to :cfunc:`PyBuffer_FromMemory`, but the returned buffer is writable.
.. cfunction:: PyObject* PyBuffer_New(Py_ssize_t size)
Return a new writable buffer object that maintains its own memory buffer of
*size* bytes. :exc:`ValueError` is returned if *size* is not zero or positive.
Note that the memory buffer (as returned by :cfunc:`PyObject_AsWriteBuffer`) is
not specifically aligned.

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.. highlightlang:: c
.. _cell-objects:
Cell Objects
------------
"Cell" objects are used to implement variables referenced by multiple scopes.
For each such variable, a cell object is created to store the value; the local
variables of each stack frame that references the value contains a reference to
the cells from outer scopes which also use that variable. When the value is
accessed, the value contained in the cell is used instead of the cell object
itself. This de-referencing of the cell object requires support from the
generated byte-code; these are not automatically de-referenced when accessed.
Cell objects are not likely to be useful elsewhere.
.. ctype:: PyCellObject
The C structure used for cell objects.
.. cvar:: PyTypeObject PyCell_Type
The type object corresponding to cell objects.
.. cfunction:: int PyCell_Check(ob)
Return true if *ob* is a cell object; *ob* must not be *NULL*.
.. cfunction:: PyObject* PyCell_New(PyObject *ob)
Create and return a new cell object containing the value *ob*. The parameter may
be *NULL*.
.. cfunction:: PyObject* PyCell_Get(PyObject *cell)
Return the contents of the cell *cell*.
.. cfunction:: PyObject* PyCell_GET(PyObject *cell)
Return the contents of the cell *cell*, but without checking that *cell* is
non-*NULL* and a cell object.
.. cfunction:: int PyCell_Set(PyObject *cell, PyObject *value)
Set the contents of the cell object *cell* to *value*. This releases the
reference to any current content of the cell. *value* may be *NULL*. *cell*
must be non-*NULL*; if it is not a cell object, ``-1`` will be returned. On
success, ``0`` will be returned.
.. cfunction:: void PyCell_SET(PyObject *cell, PyObject *value)
Sets the value of the cell object *cell* to *value*. No reference counts are
adjusted, and no checks are made for safety; *cell* must be non-*NULL* and must
be a cell object.

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.. highlightlang:: c
.. _cobjects:
CObjects
--------
.. index:: object: CObject
Refer to :ref:`using-cobjects` for more information on using these objects.
.. ctype:: PyCObject
This subtype of :ctype:`PyObject` represents an opaque value, useful for C
extension modules who need to pass an opaque value (as a :ctype:`void\*`
pointer) through Python code to other C code. It is often used to make a C
function pointer defined in one module available to other modules, so the
regular import mechanism can be used to access C APIs defined in dynamically
loaded modules.
.. cfunction:: int PyCObject_Check(PyObject *p)
Return true if its argument is a :ctype:`PyCObject`.
.. cfunction:: PyObject* PyCObject_FromVoidPtr(void* cobj, void (*destr)(void *))
Create a :ctype:`PyCObject` from the ``void *`` *cobj*. The *destr* function
will be called when the object is reclaimed, unless it is *NULL*.
.. cfunction:: PyObject* PyCObject_FromVoidPtrAndDesc(void* cobj, void* desc, void (*destr)(void *, void *))
Create a :ctype:`PyCObject` from the :ctype:`void \*` *cobj*. The *destr*
function will be called when the object is reclaimed. The *desc* argument can
be used to pass extra callback data for the destructor function.
.. cfunction:: void* PyCObject_AsVoidPtr(PyObject* self)
Return the object :ctype:`void \*` that the :ctype:`PyCObject` *self* was
created with.
.. cfunction:: void* PyCObject_GetDesc(PyObject* self)
Return the description :ctype:`void \*` that the :ctype:`PyCObject` *self* was
created with.
.. cfunction:: int PyCObject_SetVoidPtr(PyObject* self, void* cobj)
Set the void pointer inside *self* to *cobj*. The :ctype:`PyCObject` must not
have an associated destructor. Return true on success, false on failure.

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.. highlightlang:: c
.. _complexobjects:
Complex Number Objects
----------------------
.. index:: object: complex number
Python's complex number objects are implemented as two distinct types when
viewed from the C API: one is the Python object exposed to Python programs, and
the other is a C structure which represents the actual complex number value.
The API provides functions for working with both.
Complex Numbers as C Structures
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Note that the functions which accept these structures as parameters and return
them as results do so *by value* rather than dereferencing them through
pointers. This is consistent throughout the API.
.. ctype:: Py_complex
The C structure which corresponds to the value portion of a Python complex
number object. Most of the functions for dealing with complex number objects
use structures of this type as input or output values, as appropriate. It is
defined as::
typedef struct {
double real;
double imag;
} Py_complex;
.. cfunction:: Py_complex _Py_c_sum(Py_complex left, Py_complex right)
Return the sum of two complex numbers, using the C :ctype:`Py_complex`
representation.
.. cfunction:: Py_complex _Py_c_diff(Py_complex left, Py_complex right)
Return the difference between two complex numbers, using the C
:ctype:`Py_complex` representation.
.. cfunction:: Py_complex _Py_c_neg(Py_complex complex)
Return the negation of the complex number *complex*, using the C
:ctype:`Py_complex` representation.
.. cfunction:: Py_complex _Py_c_prod(Py_complex left, Py_complex right)
Return the product of two complex numbers, using the C :ctype:`Py_complex`
representation.
.. cfunction:: Py_complex _Py_c_quot(Py_complex dividend, Py_complex divisor)
Return the quotient of two complex numbers, using the C :ctype:`Py_complex`
representation.
.. cfunction:: Py_complex _Py_c_pow(Py_complex num, Py_complex exp)
Return the exponentiation of *num* by *exp*, using the C :ctype:`Py_complex`
representation.
Complex Numbers as Python Objects
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
.. ctype:: PyComplexObject
This subtype of :ctype:`PyObject` represents a Python complex number object.
.. cvar:: PyTypeObject PyComplex_Type
This instance of :ctype:`PyTypeObject` represents the Python complex number
type. It is the same object as ``complex`` and ``types.ComplexType``.
.. cfunction:: int PyComplex_Check(PyObject *p)
Return true if its argument is a :ctype:`PyComplexObject` or a subtype of
:ctype:`PyComplexObject`.
.. cfunction:: int PyComplex_CheckExact(PyObject *p)
Return true if its argument is a :ctype:`PyComplexObject`, but not a subtype of
:ctype:`PyComplexObject`.
.. cfunction:: PyObject* PyComplex_FromCComplex(Py_complex v)
Create a new Python complex number object from a C :ctype:`Py_complex` value.
.. cfunction:: PyObject* PyComplex_FromDoubles(double real, double imag)
Return a new :ctype:`PyComplexObject` object from *real* and *imag*.
.. cfunction:: double PyComplex_RealAsDouble(PyObject *op)
Return the real part of *op* as a C :ctype:`double`.
.. cfunction:: double PyComplex_ImagAsDouble(PyObject *op)
Return the imaginary part of *op* as a C :ctype:`double`.
.. cfunction:: Py_complex PyComplex_AsCComplex(PyObject *op)
Return the :ctype:`Py_complex` value of the complex number *op*.
If *op* is not a Python complex number object but has a :meth:`__complex__`
method, this method will first be called to convert *op* to a Python complex
number object.

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.. highlightlang:: c
.. _string-conversion:
String conversion and formatting
================================
Functions for number conversion and formatted string output.
.. cfunction:: int PyOS_snprintf(char *str, size_t size, const char *format, ...)
Output not more than *size* bytes to *str* according to the format string
*format* and the extra arguments. See the Unix man page :manpage:`snprintf(2)`.
.. cfunction:: int PyOS_vsnprintf(char *str, size_t size, const char *format, va_list va)
Output not more than *size* bytes to *str* according to the format string
*format* and the variable argument list *va*. Unix man page
:manpage:`vsnprintf(2)`.
:cfunc:`PyOS_snprintf` and :cfunc:`PyOS_vsnprintf` wrap the Standard C library
functions :cfunc:`snprintf` and :cfunc:`vsnprintf`. Their purpose is to
guarantee consistent behavior in corner cases, which the Standard C functions do
not.
The wrappers ensure that *str*[*size*-1] is always ``'\0'`` upon return. They
never write more than *size* bytes (including the trailing ``'\0'``) into str.
Both functions require that ``str != NULL``, ``size > 0`` and ``format !=
NULL``.
If the platform doesn't have :cfunc:`vsnprintf` and the buffer size needed to
avoid truncation exceeds *size* by more than 512 bytes, Python aborts with a
*Py_FatalError*.
The return value (*rv*) for these functions should be interpreted as follows:
* When ``0 <= rv < size``, the output conversion was successful and *rv*
characters were written to *str* (excluding the trailing ``'\0'`` byte at
*str*[*rv*]).
* When ``rv >= size``, the output conversion was truncated and a buffer with
``rv + 1`` bytes would have been needed to succeed. *str*[*size*-1] is ``'\0'``
in this case.
* When ``rv < 0``, "something bad happened." *str*[*size*-1] is ``'\0'`` in
this case too, but the rest of *str* is undefined. The exact cause of the error
depends on the underlying platform.
The following functions provide locale-independent string to number conversions.
.. cfunction:: double PyOS_ascii_strtod(const char *nptr, char **endptr)
Convert a string to a :ctype:`double`. This function behaves like the Standard C
function :cfunc:`strtod` does in the C locale. It does this without changing the
current locale, since that would not be thread-safe.
:cfunc:`PyOS_ascii_strtod` should typically be used for reading configuration
files or other non-user input that should be locale independent.
See the Unix man page :manpage:`strtod(2)` for details.
.. cfunction:: char * PyOS_ascii_formatd(char *buffer, size_t buf_len, const char *format, double d)
Convert a :ctype:`double` to a string using the ``'.'`` as the decimal
separator. *format* is a :cfunc:`printf`\ -style format string specifying the
number format. Allowed conversion characters are ``'e'``, ``'E'``, ``'f'``,
``'F'``, ``'g'`` and ``'G'``.
The return value is a pointer to *buffer* with the converted string or NULL if
the conversion failed.
.. cfunction:: double PyOS_ascii_atof(const char *nptr)
Convert a string to a :ctype:`double` in a locale-independent way.
See the Unix man page :manpage:`atof(2)` for details.
.. cfunction:: char * PyOS_stricmp(char *s1, char *s2)
Case insensitive comparsion of strings. The functions works almost
identical to :cfunc:`strcmp` except that it ignores the case.
.. cfunction:: char * PyOS_strnicmp(char *s1, char *s2, Py_ssize_t size)
Case insensitive comparsion of strings. The functions works almost
identical to :cfunc:`strncmp` except that it ignores the case.

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.. highlightlang:: c
.. _datetimeobjects:
DateTime Objects
----------------
Various date and time objects are supplied by the :mod:`datetime` module.
Before using any of these functions, the header file :file:`datetime.h` must be
included in your source (note that this is not included by :file:`Python.h`),
and the macro :cfunc:`PyDateTime_IMPORT` must be invoked. The macro puts a
pointer to a C structure into a static variable, ``PyDateTimeAPI``, that is
used by the following macros.
Type-check macros:
.. cfunction:: int PyDate_Check(PyObject *ob)
Return true if *ob* is of type :cdata:`PyDateTime_DateType` or a subtype of
:cdata:`PyDateTime_DateType`. *ob* must not be *NULL*.
.. cfunction:: int PyDate_CheckExact(PyObject *ob)
Return true if *ob* is of type :cdata:`PyDateTime_DateType`. *ob* must not be
*NULL*.
.. cfunction:: int PyDateTime_Check(PyObject *ob)
Return true if *ob* is of type :cdata:`PyDateTime_DateTimeType` or a subtype of
:cdata:`PyDateTime_DateTimeType`. *ob* must not be *NULL*.
.. cfunction:: int PyDateTime_CheckExact(PyObject *ob)
Return true if *ob* is of type :cdata:`PyDateTime_DateTimeType`. *ob* must not
be *NULL*.
.. cfunction:: int PyTime_Check(PyObject *ob)
Return true if *ob* is of type :cdata:`PyDateTime_TimeType` or a subtype of
:cdata:`PyDateTime_TimeType`. *ob* must not be *NULL*.
.. cfunction:: int PyTime_CheckExact(PyObject *ob)
Return true if *ob* is of type :cdata:`PyDateTime_TimeType`. *ob* must not be
*NULL*.
.. cfunction:: int PyDelta_Check(PyObject *ob)
Return true if *ob* is of type :cdata:`PyDateTime_DeltaType` or a subtype of
:cdata:`PyDateTime_DeltaType`. *ob* must not be *NULL*.
.. cfunction:: int PyDelta_CheckExact(PyObject *ob)
Return true if *ob* is of type :cdata:`PyDateTime_DeltaType`. *ob* must not be
*NULL*.
.. cfunction:: int PyTZInfo_Check(PyObject *ob)
Return true if *ob* is of type :cdata:`PyDateTime_TZInfoType` or a subtype of
:cdata:`PyDateTime_TZInfoType`. *ob* must not be *NULL*.
.. cfunction:: int PyTZInfo_CheckExact(PyObject *ob)
Return true if *ob* is of type :cdata:`PyDateTime_TZInfoType`. *ob* must not be
*NULL*.
Macros to create objects:
.. cfunction:: PyObject* PyDate_FromDate(int year, int month, int day)
Return a ``datetime.date`` object with the specified year, month and day.
.. cfunction:: PyObject* PyDateTime_FromDateAndTime(int year, int month, int day, int hour, int minute, int second, int usecond)
Return a ``datetime.datetime`` object with the specified year, month, day, hour,
minute, second and microsecond.
.. cfunction:: PyObject* PyTime_FromTime(int hour, int minute, int second, int usecond)
Return a ``datetime.time`` object with the specified hour, minute, second and
microsecond.
.. cfunction:: PyObject* PyDelta_FromDSU(int days, int seconds, int useconds)
Return a ``datetime.timedelta`` object representing the given number of days,
seconds and microseconds. Normalization is performed so that the resulting
number of microseconds and seconds lie in the ranges documented for
``datetime.timedelta`` objects.
Macros to extract fields from date objects. The argument must be an instance of
:cdata:`PyDateTime_Date`, including subclasses (such as
:cdata:`PyDateTime_DateTime`). The argument must not be *NULL*, and the type is
not checked:
.. cfunction:: int PyDateTime_GET_YEAR(PyDateTime_Date *o)
Return the year, as a positive int.
.. cfunction:: int PyDateTime_GET_MONTH(PyDateTime_Date *o)
Return the month, as an int from 1 through 12.
.. cfunction:: int PyDateTime_GET_DAY(PyDateTime_Date *o)
Return the day, as an int from 1 through 31.
Macros to extract fields from datetime objects. The argument must be an
instance of :cdata:`PyDateTime_DateTime`, including subclasses. The argument
must not be *NULL*, and the type is not checked:
.. cfunction:: int PyDateTime_DATE_GET_HOUR(PyDateTime_DateTime *o)
Return the hour, as an int from 0 through 23.
.. cfunction:: int PyDateTime_DATE_GET_MINUTE(PyDateTime_DateTime *o)
Return the minute, as an int from 0 through 59.
.. cfunction:: int PyDateTime_DATE_GET_SECOND(PyDateTime_DateTime *o)
Return the second, as an int from 0 through 59.
.. cfunction:: int PyDateTime_DATE_GET_MICROSECOND(PyDateTime_DateTime *o)
Return the microsecond, as an int from 0 through 999999.
Macros to extract fields from time objects. The argument must be an instance of
:cdata:`PyDateTime_Time`, including subclasses. The argument must not be *NULL*,
and the type is not checked:
.. cfunction:: int PyDateTime_TIME_GET_HOUR(PyDateTime_Time *o)
Return the hour, as an int from 0 through 23.
.. cfunction:: int PyDateTime_TIME_GET_MINUTE(PyDateTime_Time *o)
Return the minute, as an int from 0 through 59.
.. cfunction:: int PyDateTime_TIME_GET_SECOND(PyDateTime_Time *o)
Return the second, as an int from 0 through 59.
.. cfunction:: int PyDateTime_TIME_GET_MICROSECOND(PyDateTime_Time *o)
Return the microsecond, as an int from 0 through 999999.
Macros for the convenience of modules implementing the DB API:
.. cfunction:: PyObject* PyDateTime_FromTimestamp(PyObject *args)
Create and return a new ``datetime.datetime`` object given an argument tuple
suitable for passing to ``datetime.datetime.fromtimestamp()``.
.. cfunction:: PyObject* PyDate_FromTimestamp(PyObject *args)
Create and return a new ``datetime.date`` object given an argument tuple
suitable for passing to ``datetime.date.fromtimestamp()``.

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.. highlightlang:: c
.. _descriptor-objects:
Descriptor Objects
------------------
"Descriptors" are objects that describe some attribute of an object. They are
found in the dictionary of type objects.
.. XXX document these!
.. cvar:: PyTypeObject PyProperty_Type
The type object for the built-in descriptor types.
.. cfunction:: PyObject* PyDescr_NewGetSet(PyTypeObject *type, struct PyGetSetDef *getset)
.. cfunction:: PyObject* PyDescr_NewMember(PyTypeObject *type, struct PyMemberDef *meth)
.. cfunction:: PyObject* PyDescr_NewMethod(PyTypeObject *type, struct PyMethodDef *meth)
.. cfunction:: PyObject* PyDescr_NewWrapper(PyTypeObject *type, struct wrapperbase *wrapper, void *wrapped)
.. cfunction:: PyObject* PyDescr_NewClassMethod(PyTypeObject *type, PyMethodDef *method)
.. cfunction:: int PyDescr_IsData(PyObject *descr)
Return true if the descriptor objects *descr* describes a data attribute, or
false if it describes a method. *descr* must be a descriptor object; there is
no error checking.
.. cfunction:: PyObject* PyWrapper_New(PyObject *, PyObject *)

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.. highlightlang:: c
.. _dictobjects:
Dictionary Objects
------------------
.. index:: object: dictionary
.. ctype:: PyDictObject
This subtype of :ctype:`PyObject` represents a Python dictionary object.
.. cvar:: PyTypeObject PyDict_Type
.. index::
single: DictType (in module types)
single: DictionaryType (in module types)
This instance of :ctype:`PyTypeObject` represents the Python dictionary type.
This is exposed to Python programs as ``dict`` and ``types.DictType``.
.. cfunction:: int PyDict_Check(PyObject *p)
Return true if *p* is a dict object or an instance of a subtype of the dict
type.
.. cfunction:: int PyDict_CheckExact(PyObject *p)
Return true if *p* is a dict object, but not an instance of a subtype of the
dict type.
.. cfunction:: PyObject* PyDict_New()
Return a new empty dictionary, or *NULL* on failure.
.. cfunction:: PyObject* PyDictProxy_New(PyObject *dict)
Return a proxy object for a mapping which enforces read-only behavior. This is
normally used to create a proxy to prevent modification of the dictionary for
non-dynamic class types.
.. cfunction:: void PyDict_Clear(PyObject *p)
Empty an existing dictionary of all key-value pairs.
.. cfunction:: int PyDict_Contains(PyObject *p, PyObject *key)
Determine if dictionary *p* contains *key*. If an item in *p* is matches *key*,
return ``1``, otherwise return ``0``. On error, return ``-1``. This is
equivalent to the Python expression ``key in p``.
.. cfunction:: PyObject* PyDict_Copy(PyObject *p)
Return a new dictionary that contains the same key-value pairs as *p*.
.. cfunction:: int PyDict_SetItem(PyObject *p, PyObject *key, PyObject *val)
Insert *value* into the dictionary *p* with a key of *key*. *key* must be
:term:`hashable`; if it isn't, :exc:`TypeError` will be raised. Return ``0``
on success or ``-1`` on failure.
.. cfunction:: int PyDict_SetItemString(PyObject *p, const char *key, PyObject *val)
.. index:: single: PyString_FromString()
Insert *value* into the dictionary *p* using *key* as a key. *key* should be a
:ctype:`char\*`. The key object is created using ``PyString_FromString(key)``.
Return ``0`` on success or ``-1`` on failure.
.. cfunction:: int PyDict_DelItem(PyObject *p, PyObject *key)
Remove the entry in dictionary *p* with key *key*. *key* must be hashable; if it
isn't, :exc:`TypeError` is raised. Return ``0`` on success or ``-1`` on
failure.
.. cfunction:: int PyDict_DelItemString(PyObject *p, char *key)
Remove the entry in dictionary *p* which has a key specified by the string
*key*. Return ``0`` on success or ``-1`` on failure.
.. cfunction:: PyObject* PyDict_GetItem(PyObject *p, PyObject *key)
Return the object from dictionary *p* which has a key *key*. Return *NULL* if
the key *key* is not present, but *without* setting an exception.
.. cfunction:: PyObject* PyDict_GetItemString(PyObject *p, const char *key)
This is the same as :cfunc:`PyDict_GetItem`, but *key* is specified as a
:ctype:`char\*`, rather than a :ctype:`PyObject\*`.
.. cfunction:: PyObject* PyDict_Items(PyObject *p)
Return a :ctype:`PyListObject` containing all the items from the dictionary, as
in the dictionary method :meth:`dict.items`.
.. cfunction:: PyObject* PyDict_Keys(PyObject *p)
Return a :ctype:`PyListObject` containing all the keys from the dictionary, as
in the dictionary method :meth:`dict.keys`.
.. cfunction:: PyObject* PyDict_Values(PyObject *p)
Return a :ctype:`PyListObject` containing all the values from the dictionary
*p*, as in the dictionary method :meth:`dict.values`.
.. cfunction:: Py_ssize_t PyDict_Size(PyObject *p)
.. index:: builtin: len
Return the number of items in the dictionary. This is equivalent to ``len(p)``
on a dictionary.
.. cfunction:: int PyDict_Next(PyObject *p, Py_ssize_t *ppos, PyObject **pkey, PyObject **pvalue)
Iterate over all key-value pairs in the dictionary *p*. The :ctype:`int`
referred to by *ppos* must be initialized to ``0`` prior to the first call to
this function to start the iteration; the function returns true for each pair in
the dictionary, and false once all pairs have been reported. The parameters
*pkey* and *pvalue* should either point to :ctype:`PyObject\*` variables that
will be filled in with each key and value, respectively, or may be *NULL*. Any
references returned through them are borrowed. *ppos* should not be altered
during iteration. Its value represents offsets within the internal dictionary
structure, and since the structure is sparse, the offsets are not consecutive.
For example::
PyObject *key, *value;
Py_ssize_t pos = 0;
while (PyDict_Next(self->dict, &pos, &key, &value)) {
/* do something interesting with the values... */
...
}
The dictionary *p* should not be mutated during iteration. It is safe (since
Python 2.1) to modify the values of the keys as you iterate over the dictionary,
but only so long as the set of keys does not change. For example::
PyObject *key, *value;
Py_ssize_t pos = 0;
while (PyDict_Next(self->dict, &pos, &key, &value)) {
long i = PyLong_AsLong(value);
if (i == -1 && PyErr_Occurred()) {
return -1;
}
PyObject *o = PyLong_FromLong(i + 1);
if (o == NULL)
return -1;
if (PyDict_SetItem(self->dict, key, o) < 0) {
Py_DECREF(o);
return -1;
}
Py_DECREF(o);
}
.. cfunction:: int PyDict_Merge(PyObject *a, PyObject *b, int override)
Iterate over mapping object *b* adding key-value pairs to dictionary *a*. *b*
may be a dictionary, or any object supporting :func:`PyMapping_Keys` and
:func:`PyObject_GetItem`. If *override* is true, existing pairs in *a* will be
replaced if a matching key is found in *b*, otherwise pairs will only be added
if there is not a matching key in *a*. Return ``0`` on success or ``-1`` if an
exception was raised.
.. cfunction:: int PyDict_Update(PyObject *a, PyObject *b)
This is the same as ``PyDict_Merge(a, b, 1)`` in C, or ``a.update(b)`` in
Python. Return ``0`` on success or ``-1`` if an exception was raised.
.. cfunction:: int PyDict_MergeFromSeq2(PyObject *a, PyObject *seq2, int override)
Update or merge into dictionary *a*, from the key-value pairs in *seq2*. *seq2*
must be an iterable object producing iterable objects of length 2, viewed as
key-value pairs. In case of duplicate keys, the last wins if *override* is
true, else the first wins. Return ``0`` on success or ``-1`` if an exception was
raised. Equivalent Python (except for the return value)::
def PyDict_MergeFromSeq2(a, seq2, override):
for key, value in seq2:
if override or key not in a:
a[key] = value

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.. highlightlang:: c
.. _fileobjects:
File Objects
------------
.. index:: object: file
Python's built-in file objects are implemented entirely on the :ctype:`FILE\*`
support from the C standard library. This is an implementation detail and may
change in future releases of Python.
.. ctype:: PyFileObject
This subtype of :ctype:`PyObject` represents a Python file object.
.. cvar:: PyTypeObject PyFile_Type
.. index:: single: FileType (in module types)
This instance of :ctype:`PyTypeObject` represents the Python file type. This is
exposed to Python programs as ``file`` and ``types.FileType``.
.. cfunction:: int PyFile_Check(PyObject *p)
Return true if its argument is a :ctype:`PyFileObject` or a subtype of
:ctype:`PyFileObject`.
.. cfunction:: int PyFile_CheckExact(PyObject *p)
Return true if its argument is a :ctype:`PyFileObject`, but not a subtype of
:ctype:`PyFileObject`.
.. cfunction:: PyFile_FromFd(int fd, char *name, char *mode, int buffering, char *encoding, char *newline, int closefd)
Create a new :ctype:`PyFileObject` from the file descriptor of an already
opened file *fd*. The arguments *name*, *encoding* and *newline* can be
*NULL* to use the defaults; *buffering* can be *-1* to use the default.
Return *NULL* on failure.
.. warning::
Take care when you are mixing streams and descriptors! For more
information, see `the GNU C Library docs
<http://www.gnu.org/software/libc/manual/html_node/Stream_002fDescriptor-Precautions.html#Stream_002fDescriptor-Precautions>`_.
.. cfunction:: int PyObject_AsFileDescriptor(PyObject *p)
Return the file descriptor associated with *p* as an :ctype:`int`. If the
object is an integer, its value is returned. If not, the
object's :meth:`fileno` method is called if it exists; the method must return
an integer, which is returned as the file descriptor value. Sets an
exception and returns ``-1`` on failure.
.. cfunction:: PyObject* PyFile_GetLine(PyObject *p, int n)
.. index:: single: EOFError (built-in exception)
Equivalent to ``p.readline([n])``, this function reads one line from the
object *p*. *p* may be a file object or any object with a :meth:`readline`
method. If *n* is ``0``, exactly one line is read, regardless of the length of
the line. If *n* is greater than ``0``, no more than *n* bytes will be read
from the file; a partial line can be returned. In both cases, an empty string
is returned if the end of the file is reached immediately. If *n* is less than
``0``, however, one line is read regardless of length, but :exc:`EOFError` is
raised if the end of the file is reached immediately.
.. cfunction:: PyObject* PyFile_Name(PyObject *p)
Return the name of the file specified by *p* as a string object.
.. cfunction:: void PyFile_SetBufSize(PyFileObject *p, int n)
.. index:: single: setvbuf()
Available on systems with :cfunc:`setvbuf` only. This should only be called
immediately after file object creation.
.. cfunction:: int PyFile_SetEncoding(PyFileObject *p, const char *enc)
Set the file's encoding for Unicode output to *enc*. Return 1 on success and 0
on failure.
.. cfunction:: int PyFile_SoftSpace(PyObject *p, int newflag)
.. index:: single: softspace (file attribute)
This function exists for internal use by the interpreter. Set the
:attr:`softspace` attribute of *p* to *newflag* and return the previous value.
*p* does not have to be a file object for this function to work properly; any
object is supported (thought its only interesting if the :attr:`softspace`
attribute can be set). This function clears any errors, and will return ``0``
as the previous value if the attribute either does not exist or if there were
errors in retrieving it. There is no way to detect errors from this function,
but doing so should not be needed.
.. cfunction:: int PyFile_WriteObject(PyObject *obj, PyObject *p, int flags)
.. index:: single: Py_PRINT_RAW
Write object *obj* to file object *p*. The only supported flag for *flags* is
:const:`Py_PRINT_RAW`; if given, the :func:`str` of the object is written
instead of the :func:`repr`. Return ``0`` on success or ``-1`` on failure; the
appropriate exception will be set.
.. cfunction:: int PyFile_WriteString(const char *s, PyObject *p)
Write string *s* to file object *p*. Return ``0`` on success or ``-1`` on
failure; the appropriate exception will be set.

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.. highlightlang:: c
.. _floatobjects:
Floating Point Objects
----------------------
.. index:: object: floating point
.. ctype:: PyFloatObject
This subtype of :ctype:`PyObject` represents a Python floating point object.
.. cvar:: PyTypeObject PyFloat_Type
.. index:: single: FloatType (in modules types)
This instance of :ctype:`PyTypeObject` represents the Python floating point
type. This is the same object as ``float`` and ``types.FloatType``.
.. cfunction:: int PyFloat_Check(PyObject *p)
Return true if its argument is a :ctype:`PyFloatObject` or a subtype of
:ctype:`PyFloatObject`.
.. cfunction:: int PyFloat_CheckExact(PyObject *p)
Return true if its argument is a :ctype:`PyFloatObject`, but not a subtype of
:ctype:`PyFloatObject`.
.. cfunction:: PyObject* PyFloat_FromString(PyObject *str)
Create a :ctype:`PyFloatObject` object based on the string value in *str*, or
*NULL* on failure.
.. cfunction:: PyObject* PyFloat_FromDouble(double v)
Create a :ctype:`PyFloatObject` object from *v*, or *NULL* on failure.
.. cfunction:: double PyFloat_AsDouble(PyObject *pyfloat)
Return a C :ctype:`double` representation of the contents of *pyfloat*. If
*pyfloat* is not a Python floating point object but has a :meth:`__float__`
method, this method will first be called to convert *pyfloat* into a float.
.. cfunction:: double PyFloat_AS_DOUBLE(PyObject *pyfloat)
Return a C :ctype:`double` representation of the contents of *pyfloat*, but
without error checking.
.. cfunction:: PyObject* PyFloat_GetInfo(void)
Return a structseq instance which contains information about the
precision, minimum and maximum values of a float. It's a thin wrapper
around the header file :file:`float.h`.
.. cfunction:: double PyFloat_GetMax(void)
Return the maximum representable finite float *DBL_MAX* as C :ctype:`double`.
.. cfunction:: double PyFloat_GetMin(void)
Return the minimum normalized positive float *DBL_MIN* as C :ctype:`double`.

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.. highlightlang:: c
.. _function-objects:
Function Objects
----------------
.. index:: object: function
There are a few functions specific to Python functions.
.. ctype:: PyFunctionObject
The C structure used for functions.
.. cvar:: PyTypeObject PyFunction_Type
.. index:: single: MethodType (in module types)
This is an instance of :ctype:`PyTypeObject` and represents the Python function
type. It is exposed to Python programmers as ``types.FunctionType``.
.. cfunction:: int PyFunction_Check(PyObject *o)
Return true if *o* is a function object (has type :cdata:`PyFunction_Type`).
The parameter must not be *NULL*.
.. cfunction:: PyObject* PyFunction_New(PyObject *code, PyObject *globals)
Return a new function object associated with the code object *code*. *globals*
must be a dictionary with the global variables accessible to the function.
The function's docstring, name and *__module__* are retrieved from the code
object, the argument defaults and closure are set to *NULL*.
.. cfunction:: PyObject* PyFunction_GetCode(PyObject *op)
Return the code object associated with the function object *op*.
.. cfunction:: PyObject* PyFunction_GetGlobals(PyObject *op)
Return the globals dictionary associated with the function object *op*.
.. cfunction:: PyObject* PyFunction_GetModule(PyObject *op)
Return the *__module__* attribute of the function object *op*. This is normally
a string containing the module name, but can be set to any other object by
Python code.
.. cfunction:: PyObject* PyFunction_GetDefaults(PyObject *op)
Return the argument default values of the function object *op*. This can be a
tuple of arguments or *NULL*.
.. cfunction:: int PyFunction_SetDefaults(PyObject *op, PyObject *defaults)
Set the argument default values for the function object *op*. *defaults* must be
*Py_None* or a tuple.
Raises :exc:`SystemError` and returns ``-1`` on failure.
.. cfunction:: PyObject* PyFunction_GetClosure(PyObject *op)
Return the closure associated with the function object *op*. This can be *NULL*
or a tuple of cell objects.
.. cfunction:: int PyFunction_SetClosure(PyObject *op, PyObject *closure)
Set the closure associated with the function object *op*. *closure* must be
*Py_None* or a tuple of cell objects.
Raises :exc:`SystemError` and returns ``-1`` on failure.

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.. highlightlang:: c
.. _supporting-cycle-detection:
Supporting Cyclic Garbage Collection
====================================
Python's support for detecting and collecting garbage which involves circular
references requires support from object types which are "containers" for other
objects which may also be containers. Types which do not store references to
other objects, or which only store references to atomic types (such as numbers
or strings), do not need to provide any explicit support for garbage collection.
To create a container type, the :attr:`tp_flags` field of the type object must
include the :const:`Py_TPFLAGS_HAVE_GC` and provide an implementation of the
:attr:`tp_traverse` handler. If instances of the type are mutable, a
:attr:`tp_clear` implementation must also be provided.
.. data:: Py_TPFLAGS_HAVE_GC
Objects with a type with this flag set must conform with the rules documented
here. For convenience these objects will be referred to as container objects.
Constructors for container types must conform to two rules:
#. The memory for the object must be allocated using :cfunc:`PyObject_GC_New` or
:cfunc:`PyObject_GC_VarNew`.
#. Once all the fields which may contain references to other containers are
initialized, it must call :cfunc:`PyObject_GC_Track`.
.. cfunction:: TYPE* PyObject_GC_New(TYPE, PyTypeObject *type)
Analogous to :cfunc:`PyObject_New` but for container objects with the
:const:`Py_TPFLAGS_HAVE_GC` flag set.
.. cfunction:: TYPE* PyObject_GC_NewVar(TYPE, PyTypeObject *type, Py_ssize_t size)
Analogous to :cfunc:`PyObject_NewVar` but for container objects with the
:const:`Py_TPFLAGS_HAVE_GC` flag set.
.. cfunction:: PyVarObject * PyObject_GC_Resize(PyVarObject *op, Py_ssize_t)
Resize an object allocated by :cfunc:`PyObject_NewVar`. Returns the resized
object or *NULL* on failure.
.. cfunction:: void PyObject_GC_Track(PyObject *op)
Adds the object *op* to the set of container objects tracked by the collector.
The collector can run at unexpected times so objects must be valid while being
tracked. This should be called once all the fields followed by the
:attr:`tp_traverse` handler become valid, usually near the end of the
constructor.
.. cfunction:: void _PyObject_GC_TRACK(PyObject *op)
A macro version of :cfunc:`PyObject_GC_Track`. It should not be used for
extension modules.
Similarly, the deallocator for the object must conform to a similar pair of
rules:
#. Before fields which refer to other containers are invalidated,
:cfunc:`PyObject_GC_UnTrack` must be called.
#. The object's memory must be deallocated using :cfunc:`PyObject_GC_Del`.
.. cfunction:: void PyObject_GC_Del(void *op)
Releases memory allocated to an object using :cfunc:`PyObject_GC_New` or
:cfunc:`PyObject_GC_NewVar`.
.. cfunction:: void PyObject_GC_UnTrack(void *op)
Remove the object *op* from the set of container objects tracked by the
collector. Note that :cfunc:`PyObject_GC_Track` can be called again on this
object to add it back to the set of tracked objects. The deallocator
(:attr:`tp_dealloc` handler) should call this for the object before any of the
fields used by the :attr:`tp_traverse` handler become invalid.
.. cfunction:: void _PyObject_GC_UNTRACK(PyObject *op)
A macro version of :cfunc:`PyObject_GC_UnTrack`. It should not be used for
extension modules.
The :attr:`tp_traverse` handler accepts a function parameter of this type:
.. ctype:: int (*visitproc)(PyObject *object, void *arg)
Type of the visitor function passed to the :attr:`tp_traverse` handler. The
function should be called with an object to traverse as *object* and the third
parameter to the :attr:`tp_traverse` handler as *arg*. The Python core uses
several visitor functions to implement cyclic garbage detection; it's not
expected that users will need to write their own visitor functions.
The :attr:`tp_traverse` handler must have the following type:
.. ctype:: int (*traverseproc)(PyObject *self, visitproc visit, void *arg)
Traversal function for a container object. Implementations must call the
*visit* function for each object directly contained by *self*, with the
parameters to *visit* being the contained object and the *arg* value passed to
the handler. The *visit* function must not be called with a *NULL* object
argument. If *visit* returns a non-zero value that value should be returned
immediately.
To simplify writing :attr:`tp_traverse` handlers, a :cfunc:`Py_VISIT` macro is
provided. In order to use this macro, the :attr:`tp_traverse` implementation
must name its arguments exactly *visit* and *arg*:
.. cfunction:: void Py_VISIT(PyObject *o)
Call the *visit* callback, with arguments *o* and *arg*. If *visit* returns a
non-zero value, then return it. Using this macro, :attr:`tp_traverse` handlers
look like::
static int
my_traverse(Noddy *self, visitproc visit, void *arg)
{
Py_VISIT(self->foo);
Py_VISIT(self->bar);
return 0;
}
The :attr:`tp_clear` handler must be of the :ctype:`inquiry` type, or *NULL* if
the object is immutable.
.. ctype:: int (*inquiry)(PyObject *self)
Drop references that may have created reference cycles. Immutable objects do
not have to define this method since they can never directly create reference
cycles. Note that the object must still be valid after calling this method
(don't just call :cfunc:`Py_DECREF` on a reference). The collector will call
this method if it detects that this object is involved in a reference cycle.

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.. highlightlang:: c
.. _gen-objects:
Generator Objects
-----------------
Generator objects are what Python uses to implement generator iterators. They
are normally created by iterating over a function that yields values, rather
than explicitly calling :cfunc:`PyGen_New`.
.. ctype:: PyGenObject
The C structure used for generator objects.
.. cvar:: PyTypeObject PyGen_Type
The type object corresponding to generator objects
.. cfunction:: int PyGen_Check(ob)
Return true if *ob* is a generator object; *ob* must not be *NULL*.
.. cfunction:: int PyGen_CheckExact(ob)
Return true if *ob*'s type is *PyGen_Type* is a generator object; *ob* must not
be *NULL*.
.. cfunction:: PyObject* PyGen_New(PyFrameObject *frame)
Create and return a new generator object based on the *frame* object. A
reference to *frame* is stolen by this function. The parameter must not be
*NULL*.

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.. highlightlang:: c
.. _importing:
Importing Modules
=================
.. cfunction:: PyObject* PyImport_ImportModule(const char *name)
.. index::
single: package variable; __all__
single: __all__ (package variable)
single: modules (in module sys)
This is a simplified interface to :cfunc:`PyImport_ImportModuleEx` below,
leaving the *globals* and *locals* arguments set to *NULL* and *level* set
to 0. When the *name*
argument contains a dot (when it specifies a submodule of a package), the
*fromlist* argument is set to the list ``['*']`` so that the return value is the
named module rather than the top-level package containing it as would otherwise
be the case. (Unfortunately, this has an additional side effect when *name* in
fact specifies a subpackage instead of a submodule: the submodules specified in
the package's ``__all__`` variable are loaded.) Return a new reference to the
imported module, or *NULL* with an exception set on failure. Before Python 2.4,
the module may still be created in the failure case --- examine ``sys.modules``
to find out. Starting with Python 2.4, a failing import of a module no longer
leaves the module in ``sys.modules``.
.. cfunction:: PyObject* PyImport_ImportModuleNoBlock(const char *name)
This version of :cfunc:`PyImport_ImportModule` does not block. It's intended
to be used in C functions that import other modules to execute a function.
The import may block if another thread holds the import lock. The function
:cfunc:`PyImport_ImportModuleNoBlock` never blocks. It first tries to fetch
the module from sys.modules and falls back to :cfunc:`PyImport_ImportModule`
unless the lock is held, in which case the function will raise an
:exc:`ImportError`.
.. cfunction:: PyObject* PyImport_ImportModuleEx(char *name, PyObject *globals, PyObject *locals, PyObject *fromlist)
.. index:: builtin: __import__
Import a module. This is best described by referring to the built-in Python
function :func:`__import__`, as the standard :func:`__import__` function calls
this function directly.
The return value is a new reference to the imported module or top-level package,
or *NULL* with an exception set on failure (before Python 2.4, the module may
still be created in this case). Like for :func:`__import__`, the return value
when a submodule of a package was requested is normally the top-level package,
unless a non-empty *fromlist* was given.
Failing imports remove incomplete module objects, like with
:cfunc:`PyImport_ImportModule`.
.. cfunction:: PyObject* PyImport_ImportModuleLevel(char *name, PyObject *globals, PyObject *locals, PyObject *fromlist, int level)
Import a module. This is best described by referring to the built-in Python
function :func:`__import__`, as the standard :func:`__import__` function calls
this function directly.
The return value is a new reference to the imported module or top-level package,
or *NULL* with an exception set on failure. Like for :func:`__import__`,
the return value when a submodule of a package was requested is normally the
top-level package, unless a non-empty *fromlist* was given.
.. cfunction:: PyObject* PyImport_Import(PyObject *name)
This is a higher-level interface that calls the current "import hook
function" (with an explicit *level* of 0, meaning absolute import). It
invokes the :func:`__import__` function from the ``__builtins__`` of the
current globals. This means that the import is done using whatever import
hooks are installed in the current environment.
.. cfunction:: PyObject* PyImport_ReloadModule(PyObject *m)
Reload a module. Return a new reference to the reloaded module, or *NULL* with
an exception set on failure (the module still exists in this case).
.. cfunction:: PyObject* PyImport_AddModule(const char *name)
Return the module object corresponding to a module name. The *name* argument
may be of the form ``package.module``. First check the modules dictionary if
there's one there, and if not, create a new one and insert it in the modules
dictionary. Return *NULL* with an exception set on failure.
.. note::
This function does not load or import the module; if the module wasn't already
loaded, you will get an empty module object. Use :cfunc:`PyImport_ImportModule`
or one of its variants to import a module. Package structures implied by a
dotted name for *name* are not created if not already present.
.. cfunction:: PyObject* PyImport_ExecCodeModule(char *name, PyObject *co)
.. index:: builtin: compile
Given a module name (possibly of the form ``package.module``) and a code object
read from a Python bytecode file or obtained from the built-in function
:func:`compile`, load the module. Return a new reference to the module object,
or *NULL* with an exception set if an error occurred. Before Python 2.4, the
module could still be created in error cases. Starting with Python 2.4, *name*
is removed from :attr:`sys.modules` in error cases, and even if *name* was already
in :attr:`sys.modules` on entry to :cfunc:`PyImport_ExecCodeModule`. Leaving
incompletely initialized modules in :attr:`sys.modules` is dangerous, as imports of
such modules have no way to know that the module object is an unknown (and
probably damaged with respect to the module author's intents) state.
This function will reload the module if it was already imported. See
:cfunc:`PyImport_ReloadModule` for the intended way to reload a module.
If *name* points to a dotted name of the form ``package.module``, any package
structures not already created will still not be created.
.. cfunction:: long PyImport_GetMagicNumber()
Return the magic number for Python bytecode files (a.k.a. :file:`.pyc` and
:file:`.pyo` files). The magic number should be present in the first four bytes
of the bytecode file, in little-endian byte order.
.. cfunction:: PyObject* PyImport_GetModuleDict()
Return the dictionary used for the module administration (a.k.a.
``sys.modules``). Note that this is a per-interpreter variable.
.. cfunction:: void _PyImport_Init()
Initialize the import mechanism. For internal use only.
.. cfunction:: void PyImport_Cleanup()
Empty the module table. For internal use only.
.. cfunction:: void _PyImport_Fini()
Finalize the import mechanism. For internal use only.
.. cfunction:: PyObject* _PyImport_FindExtension(char *, char *)
For internal use only.
.. cfunction:: PyObject* _PyImport_FixupExtension(char *, char *)
For internal use only.
.. cfunction:: int PyImport_ImportFrozenModule(char *name)
Load a frozen module named *name*. Return ``1`` for success, ``0`` if the
module is not found, and ``-1`` with an exception set if the initialization
failed. To access the imported module on a successful load, use
:cfunc:`PyImport_ImportModule`. (Note the misnomer --- this function would
reload the module if it was already imported.)
.. ctype:: struct _frozen
.. index:: single: freeze utility
This is the structure type definition for frozen module descriptors, as
generated by the :program:`freeze` utility (see :file:`Tools/freeze/` in the
Python source distribution). Its definition, found in :file:`Include/import.h`,
is::
struct _frozen {
char *name;
unsigned char *code;
int size;
};
.. cvar:: struct _frozen* PyImport_FrozenModules
This pointer is initialized to point to an array of :ctype:`struct _frozen`
records, terminated by one whose members are all *NULL* or zero. When a frozen
module is imported, it is searched in this table. Third-party code could play
tricks with this to provide a dynamically created collection of frozen modules.
.. cfunction:: int PyImport_AppendInittab(char *name, void (*initfunc)(void))
Add a single module to the existing table of built-in modules. This is a
convenience wrapper around :cfunc:`PyImport_ExtendInittab`, returning ``-1`` if
the table could not be extended. The new module can be imported by the name
*name*, and uses the function *initfunc* as the initialization function called
on the first attempted import. This should be called before
:cfunc:`Py_Initialize`.
.. ctype:: struct _inittab
Structure describing a single entry in the list of built-in modules. Each of
these structures gives the name and initialization function for a module built
into the interpreter. Programs which embed Python may use an array of these
structures in conjunction with :cfunc:`PyImport_ExtendInittab` to provide
additional built-in modules. The structure is defined in
:file:`Include/import.h` as::
struct _inittab {
char *name;
void (*initfunc)(void);
};
.. cfunction:: int PyImport_ExtendInittab(struct _inittab *newtab)
Add a collection of modules to the table of built-in modules. The *newtab*
array must end with a sentinel entry which contains *NULL* for the :attr:`name`
field; failure to provide the sentinel value can result in a memory fault.
Returns ``0`` on success or ``-1`` if insufficient memory could be allocated to
extend the internal table. In the event of failure, no modules are added to the
internal table. This should be called before :cfunc:`Py_Initialize`.

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.. highlightlang:: c
.. _iterator:
Iterator Protocol
=================
There are only a couple of functions specifically for working with iterators.
.. cfunction:: int PyIter_Check(PyObject *o)
Return true if the object *o* supports the iterator protocol.
.. cfunction:: PyObject* PyIter_Next(PyObject *o)
Return the next value from the iteration *o*. If the object is an iterator,
this retrieves the next value from the iteration, and returns *NULL* with no
exception set if there are no remaining items. If the object is not an
iterator, :exc:`TypeError` is raised, or if there is an error in retrieving the
item, returns *NULL* and passes along the exception.
To write a loop which iterates over an iterator, the C code should look
something like this::
PyObject *iterator = PyObject_GetIter(obj);
PyObject *item;
if (iterator == NULL) {
/* propagate error */
}
while (item = PyIter_Next(iterator)) {
/* do something with item */
...
/* release reference when done */
Py_DECREF(item);
}
Py_DECREF(iterator);
if (PyErr_Occurred()) {
/* propagate error */
}
else {
/* continue doing useful work */
}

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.. highlightlang:: c
.. _iterator-objects:
Iterator Objects
----------------
Python provides two general-purpose iterator objects. The first, a sequence
iterator, works with an arbitrary sequence supporting the :meth:`__getitem__`
method. The second works with a callable object and a sentinel value, calling
the callable for each item in the sequence, and ending the iteration when the
sentinel value is returned.
.. cvar:: PyTypeObject PySeqIter_Type
Type object for iterator objects returned by :cfunc:`PySeqIter_New` and the
one-argument form of the :func:`iter` built-in function for built-in sequence
types.
.. cfunction:: int PySeqIter_Check(op)
Return true if the type of *op* is :cdata:`PySeqIter_Type`.
.. cfunction:: PyObject* PySeqIter_New(PyObject *seq)
Return an iterator that works with a general sequence object, *seq*. The
iteration ends when the sequence raises :exc:`IndexError` for the subscripting
operation.
.. cvar:: PyTypeObject PyCallIter_Type
Type object for iterator objects returned by :cfunc:`PyCallIter_New` and the
two-argument form of the :func:`iter` built-in function.
.. cfunction:: int PyCallIter_Check(op)
Return true if the type of *op* is :cdata:`PyCallIter_Type`.
.. cfunction:: PyObject* PyCallIter_New(PyObject *callable, PyObject *sentinel)
Return a new iterator. The first parameter, *callable*, can be any Python
callable object that can be called with no parameters; each call to it should
return the next item in the iteration. When *callable* returns a value equal to
*sentinel*, the iteration will be terminated.

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.. highlightlang:: c
.. _listobjects:
List Objects
------------
.. index:: object: list
.. ctype:: PyListObject
This subtype of :ctype:`PyObject` represents a Python list object.
.. cvar:: PyTypeObject PyList_Type
.. index:: single: ListType (in module types)
This instance of :ctype:`PyTypeObject` represents the Python list type. This is
the same object as ``list`` and ``types.ListType`` in the Python layer.
.. cfunction:: int PyList_Check(PyObject *p)
Return true if *p* is a list object or an instance of a subtype of the list
type.
.. cfunction:: int PyList_CheckExact(PyObject *p)
Return true if *p* is a list object, but not an instance of a subtype of the
list type.
.. cfunction:: PyObject* PyList_New(Py_ssize_t len)
Return a new list of length *len* on success, or *NULL* on failure.
.. note::
If *length* is greater than zero, the returned list object's items are set to
``NULL``. Thus you cannot use abstract API functions such as
:cfunc:`PySequence_SetItem` or expose the object to Python code before setting
all items to a real object with :cfunc:`PyList_SetItem`.
.. cfunction:: Py_ssize_t PyList_Size(PyObject *list)
.. index:: builtin: len
Return the length of the list object in *list*; this is equivalent to
``len(list)`` on a list object.
.. cfunction:: Py_ssize_t PyList_GET_SIZE(PyObject *list)
Macro form of :cfunc:`PyList_Size` without error checking.
.. cfunction:: PyObject* PyList_GetItem(PyObject *list, Py_ssize_t index)
Return the object at position *pos* in the list pointed to by *p*. The position
must be positive, indexing from the end of the list is not supported. If *pos*
is out of bounds, return *NULL* and set an :exc:`IndexError` exception.
.. cfunction:: PyObject* PyList_GET_ITEM(PyObject *list, Py_ssize_t i)
Macro form of :cfunc:`PyList_GetItem` without error checking.
.. cfunction:: int PyList_SetItem(PyObject *list, Py_ssize_t index, PyObject *item)
Set the item at index *index* in list to *item*. Return ``0`` on success or
``-1`` on failure.
.. note::
This function "steals" a reference to *item* and discards a reference to an item
already in the list at the affected position.
.. cfunction:: void PyList_SET_ITEM(PyObject *list, Py_ssize_t i, PyObject *o)
Macro form of :cfunc:`PyList_SetItem` without error checking. This is normally
only used to fill in new lists where there is no previous content.
.. note::
This function "steals" a reference to *item*, and, unlike
:cfunc:`PyList_SetItem`, does *not* discard a reference to any item that it
being replaced; any reference in *list* at position *i* will be leaked.
.. cfunction:: int PyList_Insert(PyObject *list, Py_ssize_t index, PyObject *item)
Insert the item *item* into list *list* in front of index *index*. Return ``0``
if successful; return ``-1`` and set an exception if unsuccessful. Analogous to
``list.insert(index, item)``.
.. cfunction:: int PyList_Append(PyObject *list, PyObject *item)
Append the object *item* at the end of list *list*. Return ``0`` if successful;
return ``-1`` and set an exception if unsuccessful. Analogous to
``list.append(item)``.
.. cfunction:: PyObject* PyList_GetSlice(PyObject *list, Py_ssize_t low, Py_ssize_t high)
Return a list of the objects in *list* containing the objects *between* *low*
and *high*. Return *NULL* and set an exception if unsuccessful. Analogous to
``list[low:high]``.
.. cfunction:: int PyList_SetSlice(PyObject *list, Py_ssize_t low, Py_ssize_t high, PyObject *itemlist)
Set the slice of *list* between *low* and *high* to the contents of *itemlist*.
Analogous to ``list[low:high] = itemlist``. The *itemlist* may be *NULL*,
indicating the assignment of an empty list (slice deletion). Return ``0`` on
success, ``-1`` on failure.
.. cfunction:: int PyList_Sort(PyObject *list)
Sort the items of *list* in place. Return ``0`` on success, ``-1`` on failure.
This is equivalent to ``list.sort()``.
.. cfunction:: int PyList_Reverse(PyObject *list)
Reverse the items of *list* in place. Return ``0`` on success, ``-1`` on
failure. This is the equivalent of ``list.reverse()``.
.. cfunction:: PyObject* PyList_AsTuple(PyObject *list)
.. index:: builtin: tuple
Return a new tuple object containing the contents of *list*; equivalent to
``tuple(list)``.

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.. highlightlang:: c
.. _longobjects:
Integer Objects
---------------
.. index:: object: long integer
object: integer
All integers are implemented as "long" integer objects of arbitrary size.
.. ctype:: PyLongObject
This subtype of :ctype:`PyObject` represents a Python integer object.
.. cvar:: PyTypeObject PyLong_Type
This instance of :ctype:`PyTypeObject` represents the Python integer type.
This is the same object as ``int``.
.. cfunction:: int PyLong_Check(PyObject *p)
Return true if its argument is a :ctype:`PyLongObject` or a subtype of
:ctype:`PyLongObject`.
.. cfunction:: int PyLong_CheckExact(PyObject *p)
Return true if its argument is a :ctype:`PyLongObject`, but not a subtype of
:ctype:`PyLongObject`.
.. cfunction:: PyObject* PyLong_FromLong(long v)
Return a new :ctype:`PyLongObject` object from *v*, or *NULL* on failure.
The current implementation keeps an array of integer objects for all integers
between ``-5`` and ``256``, when you create an int in that range you actually
just get back a reference to the existing object. So it should be possible to
change the value of ``1``. I suspect the behaviour of Python in this case is
undefined. :-)
.. cfunction:: PyObject* PyLong_FromUnsignedLong(unsigned long v)
Return a new :ctype:`PyLongObject` object from a C :ctype:`unsigned long`, or
*NULL* on failure.
.. cfunction:: PyObject* PyLong_FromSsize_t(Py_ssize_t v)
Return a new :ctype:`PyLongObject` object with a value of *v*, or *NULL*
on failure.
.. cfunction:: PyObject* PyLong_FromSize_t(size_t v)
Return a new :ctype:`PyLongObject` object with a value of *v*, or *NULL*
on failure.
.. cfunction:: PyObject* PyLong_FromLongLong(PY_LONG_LONG v)
Return a new :ctype:`PyLongObject` object from a C :ctype:`long long`, or *NULL*
on failure.
.. cfunction:: PyObject* PyLong_FromUnsignedLongLong(unsigned PY_LONG_LONG v)
Return a new :ctype:`PyLongObject` object from a C :ctype:`unsigned long long`,
or *NULL* on failure.
.. cfunction:: PyObject* PyLong_FromDouble(double v)
Return a new :ctype:`PyLongObject` object from the integer part of *v*, or
*NULL* on failure.
.. cfunction:: PyObject* PyLong_FromString(char *str, char **pend, int base)
Return a new :ctype:`PyLongObject` based on the string value in *str*, which
is interpreted according to the radix in *base*. If *pend* is non-*NULL*,
``*pend`` will point to the first character in *str* which follows the
representation of the number. If *base* is ``0``, the radix will be
determined based on the leading characters of *str*: if *str* starts with
``'0x'`` or ``'0X'``, radix 16 will be used; if *str* starts with ``'0o'`` or
``'0O'``, radix 8 will be used; if *str* starts with ``'0b'`` or ``'0B'``,
radix 2 will be used; otherwise radix 10 will be used. If *base* is not
``0``, it must be between ``2`` and ``36``, inclusive. Leading spaces are
ignored. If there are no digits, :exc:`ValueError` will be raised.
.. cfunction:: PyObject* PyLong_FromUnicode(Py_UNICODE *u, Py_ssize_t length, int base)
Convert a sequence of Unicode digits to a Python integer value. The Unicode
string is first encoded to a byte string using :cfunc:`PyUnicode_EncodeDecimal`
and then converted using :cfunc:`PyLong_FromString`.
.. cfunction:: PyObject* PyLong_FromVoidPtr(void *p)
Create a Python integer from the pointer *p*. The pointer value can be
retrieved from the resulting value using :cfunc:`PyLong_AsVoidPtr`.
.. XXX alias PyLong_AS_LONG (for now)
.. cfunction:: long PyLong_AsLong(PyObject *pylong)
.. index::
single: LONG_MAX
single: OverflowError (built-in exception)
Return a C :ctype:`long` representation of the contents of *pylong*. If
*pylong* is greater than :const:`LONG_MAX`, raise an :exc:`OverflowError`,
and return -1. Convert non-long objects automatically to long first,
and return -1 if that raises exceptions.
.. cfunction:: long PyLong_AsLongAndOverflow(PyObject *pylong, int* overflow)
Return a C :ctype:`long` representation of the contents of *pylong*. If
*pylong* is greater than :const:`LONG_MAX`, return -1 and
set `*overflow` to 1 (for overflow) or -1 (for underflow).
If an exception is set because of type errors, also return -1.
.. cfunction:: unsigned long PyLong_AsUnsignedLong(PyObject *pylong)
.. index::
single: ULONG_MAX
single: OverflowError (built-in exception)
Return a C :ctype:`unsigned long` representation of the contents of *pylong*.
If *pylong* is greater than :const:`ULONG_MAX`, an :exc:`OverflowError` is
raised.
.. cfunction:: Py_ssize_t PyLong_AsSsize_t(PyObject *pylong)
.. index::
single: PY_SSIZE_T_MAX
Return a :ctype:`Py_ssize_t` representation of the contents of *pylong*. If
*pylong* is greater than :const:`PY_SSIZE_T_MAX`, an :exc:`OverflowError` is
raised.
.. cfunction:: size_t PyLong_AsSize_t(PyObject *pylong)
Return a :ctype:`size_t` representation of the contents of *pylong*. If
*pylong* is greater than the maximum value for a :ctype:`size_t`, an
:exc:`OverflowError` is raised.
.. cfunction:: PY_LONG_LONG PyLong_AsLongLong(PyObject *pylong)
Return a C :ctype:`long long` from a Python integer. If *pylong* cannot be
represented as a :ctype:`long long`, an :exc:`OverflowError` will be raised.
.. cfunction:: unsigned PY_LONG_LONG PyLong_AsUnsignedLongLong(PyObject *pylong)
Return a C :ctype:`unsigned long long` from a Python integer. If *pylong*
cannot be represented as an :ctype:`unsigned long long`, an :exc:`OverflowError`
will be raised if the value is positive, or a :exc:`TypeError` will be raised if
the value is negative.
.. cfunction:: unsigned long PyLong_AsUnsignedLongMask(PyObject *io)
Return a C :ctype:`unsigned long` from a Python integer, without checking for
overflow.
.. cfunction:: unsigned PY_LONG_LONG PyLong_AsUnsignedLongLongMask(PyObject *io)
Return a C :ctype:`unsigned long long` from a Python integer, without
checking for overflow.
.. cfunction:: double PyLong_AsDouble(PyObject *pylong)
Return a C :ctype:`double` representation of the contents of *pylong*. If
*pylong* cannot be approximately represented as a :ctype:`double`, an
:exc:`OverflowError` exception is raised and ``-1.0`` will be returned.
.. cfunction:: void* PyLong_AsVoidPtr(PyObject *pylong)
Convert a Python integer *pylong* to a C :ctype:`void` pointer. If *pylong*
cannot be converted, an :exc:`OverflowError` will be raised. This is only
assured to produce a usable :ctype:`void` pointer for values created with
:cfunc:`PyLong_FromVoidPtr`.

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.. highlightlang:: c
.. _mapping:
Mapping Protocol
================
.. cfunction:: int PyMapping_Check(PyObject *o)
Return ``1`` if the object provides mapping protocol, and ``0`` otherwise. This
function always succeeds.
.. cfunction:: Py_ssize_t PyMapping_Length(PyObject *o)
.. index:: builtin: len
Returns the number of keys in object *o* on success, and ``-1`` on failure. For
objects that do not provide mapping protocol, this is equivalent to the Python
expression ``len(o)``.
.. cfunction:: int PyMapping_DelItemString(PyObject *o, char *key)
Remove the mapping for object *key* from the object *o*. Return ``-1`` on
failure. This is equivalent to the Python statement ``del o[key]``.
.. cfunction:: int PyMapping_DelItem(PyObject *o, PyObject *key)
Remove the mapping for object *key* from the object *o*. Return ``-1`` on
failure. This is equivalent to the Python statement ``del o[key]``.
.. cfunction:: int PyMapping_HasKeyString(PyObject *o, char *key)
On success, return ``1`` if the mapping object has the key *key* and ``0``
otherwise. This is equivalent to the Python expression ``key in o``.
This function always succeeds.
.. cfunction:: int PyMapping_HasKey(PyObject *o, PyObject *key)
Return ``1`` if the mapping object has the key *key* and ``0`` otherwise. This
is equivalent to the Python expression ``key in o``. This function always
succeeds.
.. cfunction:: PyObject* PyMapping_Keys(PyObject *o)
On success, return a list of the keys in object *o*. On failure, return *NULL*.
This is equivalent to the Python expression ``o.keys()``.
.. cfunction:: PyObject* PyMapping_Values(PyObject *o)
On success, return a list of the values in object *o*. On failure, return
*NULL*. This is equivalent to the Python expression ``o.values()``.
.. cfunction:: PyObject* PyMapping_Items(PyObject *o)
On success, return a list of the items in object *o*, where each item is a tuple
containing a key-value pair. On failure, return *NULL*. This is equivalent to
the Python expression ``o.items()``.
.. cfunction:: PyObject* PyMapping_GetItemString(PyObject *o, char *key)
Return element of *o* corresponding to the object *key* or *NULL* on failure.
This is the equivalent of the Python expression ``o[key]``.
.. cfunction:: int PyMapping_SetItemString(PyObject *o, char *key, PyObject *v)
Map the object *key* to the value *v* in object *o*. Returns ``-1`` on failure.
This is the equivalent of the Python statement ``o[key] = v``.

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.. highlightlang:: c
.. _marshalling-utils:
Data marshalling support
========================
These routines allow C code to work with serialized objects using the same data
format as the :mod:`marshal` module. There are functions to write data into the
serialization format, and additional functions that can be used to read the data
back. Files used to store marshalled data must be opened in binary mode.
Numeric values are stored with the least significant byte first.
The module supports two versions of the data format: version 0 is the historical
version, version 1 (new in Python 2.4) shares interned strings in the file, and
upon unmarshalling. *Py_MARSHAL_VERSION* indicates the current file format
(currently 1).
.. cfunction:: void PyMarshal_WriteLongToFile(long value, FILE *file, int version)
Marshal a :ctype:`long` integer, *value*, to *file*. This will only write the
least-significant 32 bits of *value*; regardless of the size of the native
:ctype:`long` type. *version* indicates the file format.
.. cfunction:: void PyMarshal_WriteObjectToFile(PyObject *value, FILE *file, int version)
Marshal a Python object, *value*, to *file*.
*version* indicates the file format.
.. cfunction:: PyObject* PyMarshal_WriteObjectToString(PyObject *value, int version)
Return a string object containing the marshalled representation of *value*.
*version* indicates the file format.
The following functions allow marshalled values to be read back in.
XXX What about error detection? It appears that reading past the end of the
file will always result in a negative numeric value (where that's relevant), but
it's not clear that negative values won't be handled properly when there's no
error. What's the right way to tell? Should only non-negative values be written
using these routines?
.. cfunction:: long PyMarshal_ReadLongFromFile(FILE *file)
Return a C :ctype:`long` from the data stream in a :ctype:`FILE\*` opened for
reading. Only a 32-bit value can be read in using this function, regardless of
the native size of :ctype:`long`.
.. cfunction:: int PyMarshal_ReadShortFromFile(FILE *file)
Return a C :ctype:`short` from the data stream in a :ctype:`FILE\*` opened for
reading. Only a 16-bit value can be read in using this function, regardless of
the native size of :ctype:`short`.
.. cfunction:: PyObject* PyMarshal_ReadObjectFromFile(FILE *file)
Return a Python object from the data stream in a :ctype:`FILE\*` opened for
reading. On error, sets the appropriate exception (:exc:`EOFError` or
:exc:`TypeError`) and returns *NULL*.
.. cfunction:: PyObject* PyMarshal_ReadLastObjectFromFile(FILE *file)
Return a Python object from the data stream in a :ctype:`FILE\*` opened for
reading. Unlike :cfunc:`PyMarshal_ReadObjectFromFile`, this function assumes
that no further objects will be read from the file, allowing it to aggressively
load file data into memory so that the de-serialization can operate from data in
memory rather than reading a byte at a time from the file. Only use these
variant if you are certain that you won't be reading anything else from the
file. On error, sets the appropriate exception (:exc:`EOFError` or
:exc:`TypeError`) and returns *NULL*.
.. cfunction:: PyObject* PyMarshal_ReadObjectFromString(char *string, Py_ssize_t len)
Return a Python object from the data stream in a character buffer containing
*len* bytes pointed to by *string*. On error, sets the appropriate exception
(:exc:`EOFError` or :exc:`TypeError`) and returns *NULL*.

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.. highlightlang:: c
.. _instancemethod-objects:
Instance Method Objects
-----------------------
.. index:: object: instancemethod
An instance method is a wrapper for a :cdata:`PyCFunction` and the new way
to bind a :cdata:`PyCFunction` to a class object. It replaces the former call
``PyMethod_New(func, NULL, class)``.
.. cvar:: PyTypeObject PyInstanceMethod_Type
This instance of :ctype:`PyTypeObject` represents the Python instance
method type. It is not exposed to Python programs.
.. cfunction:: int PyInstanceMethod_Check(PyObject *o)
Return true if *o* is an instance method object (has type
:cdata:`PyInstanceMethod_Type`). The parameter must not be *NULL*.
.. cfunction:: PyObject* PyInstanceMethod_New(PyObject *func)
Return a new instance method object, with *func* being any callable object
*func* is is the function that will be called when the instance method is
called.
.. cfunction:: PyObject* PyInstanceMethod_Function(PyObject *im)
Return the function object associated with the instance method *im*.
.. cfunction:: PyObject* PyInstanceMethod_GET_FUNCTION(PyObject *im)
Macro version of :cfunc:`PyInstanceMethod_Function` which avoids error checking.
.. _method-objects:
Method Objects
--------------
.. index:: object: method
Methods are bound function objects. Methods are always bound to an instance of
an user-defined class. Unbound methods (methods bound to a class object) are
no longer available.
.. cvar:: PyTypeObject PyMethod_Type
.. index:: single: MethodType (in module types)
This instance of :ctype:`PyTypeObject` represents the Python method type. This
is exposed to Python programs as ``types.MethodType``.
.. cfunction:: int PyMethod_Check(PyObject *o)
Return true if *o* is a method object (has type :cdata:`PyMethod_Type`). The
parameter must not be *NULL*.
.. cfunction:: PyObject* PyMethod_New(PyObject *func, PyObject *self)
Return a new method object, with *func* being any callable object and *self*
the instance the method should be bound. *func* is is the function that will
be called when the method is called. *self* must not be *NULL*.
.. cfunction:: PyObject* PyMethod_Function(PyObject *meth)
Return the function object associated with the method *meth*.
.. cfunction:: PyObject* PyMethod_GET_FUNCTION(PyObject *meth)
Macro version of :cfunc:`PyMethod_Function` which avoids error checking.
.. cfunction:: PyObject* PyMethod_Self(PyObject *meth)
Return the instance associated with the method *meth*.
.. cfunction:: PyObject* PyMethod_GET_SELF(PyObject *meth)
Macro version of :cfunc:`PyMethod_Self` which avoids error checking.

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.. highlightlang:: c
.. _moduleobjects:
Module Objects
--------------
.. index:: object: module
There are only a few functions special to module objects.
.. cvar:: PyTypeObject PyModule_Type
.. index:: single: ModuleType (in module types)
This instance of :ctype:`PyTypeObject` represents the Python module type. This
is exposed to Python programs as ``types.ModuleType``.
.. cfunction:: int PyModule_Check(PyObject *p)
Return true if *p* is a module object, or a subtype of a module object.
.. cfunction:: int PyModule_CheckExact(PyObject *p)
Return true if *p* is a module object, but not a subtype of
:cdata:`PyModule_Type`.
.. cfunction:: PyObject* PyModule_New(const char *name)
.. index::
single: __name__ (module attribute)
single: __doc__ (module attribute)
single: __file__ (module attribute)
Return a new module object with the :attr:`__name__` attribute set to *name*.
Only the module's :attr:`__doc__` and :attr:`__name__` attributes are filled in;
the caller is responsible for providing a :attr:`__file__` attribute.
.. cfunction:: PyObject* PyModule_GetDict(PyObject *module)
.. index:: single: __dict__ (module attribute)
Return the dictionary object that implements *module*'s namespace; this object
is the same as the :attr:`__dict__` attribute of the module object. This
function never fails. It is recommended extensions use other
:cfunc:`PyModule_\*` and :cfunc:`PyObject_\*` functions rather than directly
manipulate a module's :attr:`__dict__`.
.. cfunction:: char* PyModule_GetName(PyObject *module)
.. index::
single: __name__ (module attribute)
single: SystemError (built-in exception)
Return *module*'s :attr:`__name__` value. If the module does not provide one,
or if it is not a string, :exc:`SystemError` is raised and *NULL* is returned.
.. cfunction:: char* PyModule_GetFilename(PyObject *module)
.. index::
single: __file__ (module attribute)
single: SystemError (built-in exception)
Return the name of the file from which *module* was loaded using *module*'s
:attr:`__file__` attribute. If this is not defined, or if it is not a string,
raise :exc:`SystemError` and return *NULL*.
.. cfunction:: int PyModule_AddObject(PyObject *module, const char *name, PyObject *value)
Add an object to *module* as *name*. This is a convenience function which can
be used from the module's initialization function. This steals a reference to
*value*. Return ``-1`` on error, ``0`` on success.
.. cfunction:: int PyModule_AddIntConstant(PyObject *module, const char *name, long value)
Add an integer constant to *module* as *name*. This convenience function can be
used from the module's initialization function. Return ``-1`` on error, ``0`` on
success.
.. cfunction:: int PyModule_AddStringConstant(PyObject *module, const char *name, const char *value)
Add a string constant to *module* as *name*. This convenience function can be
used from the module's initialization function. The string *value* must be
null-terminated. Return ``-1`` on error, ``0`` on success.

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.. highlightlang:: c
.. _noneobject:
The None Object
---------------
.. index:: object: None
Note that the :ctype:`PyTypeObject` for ``None`` is not directly exposed in the
Python/C API. Since ``None`` is a singleton, testing for object identity (using
``==`` in C) is sufficient. There is no :cfunc:`PyNone_Check` function for the
same reason.
.. cvar:: PyObject* Py_None
The Python ``None`` object, denoting lack of value. This object has no methods.
It needs to be treated just like any other object with respect to reference
counts.
.. cmacro:: Py_RETURN_NONE
Properly handle returning :cdata:`Py_None` from within a C function (that is,
increment the reference count of None and return it.)

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.. highlightlang:: c
.. _number:
Number Protocol
===============
.. cfunction:: int PyNumber_Check(PyObject *o)
Returns ``1`` if the object *o* provides numeric protocols, and false otherwise.
This function always succeeds.
.. cfunction:: PyObject* PyNumber_Add(PyObject *o1, PyObject *o2)
Returns the result of adding *o1* and *o2*, or *NULL* on failure. This is the
equivalent of the Python expression ``o1 + o2``.
.. cfunction:: PyObject* PyNumber_Subtract(PyObject *o1, PyObject *o2)
Returns the result of subtracting *o2* from *o1*, or *NULL* on failure. This is
the equivalent of the Python expression ``o1 - o2``.
.. cfunction:: PyObject* PyNumber_Multiply(PyObject *o1, PyObject *o2)
Returns the result of multiplying *o1* and *o2*, or *NULL* on failure. This is
the equivalent of the Python expression ``o1 * o2``.
.. cfunction:: PyObject* PyNumber_Divide(PyObject *o1, PyObject *o2)
Returns the result of dividing *o1* by *o2*, or *NULL* on failure. This is the
equivalent of the Python expression ``o1 / o2``.
.. cfunction:: PyObject* PyNumber_FloorDivide(PyObject *o1, PyObject *o2)
Return the floor of *o1* divided by *o2*, or *NULL* on failure. This is
equivalent to the "classic" division of integers.
.. cfunction:: PyObject* PyNumber_TrueDivide(PyObject *o1, PyObject *o2)
Return a reasonable approximation for the mathematical value of *o1* divided by
*o2*, or *NULL* on failure. The return value is "approximate" because binary
floating point numbers are approximate; it is not possible to represent all real
numbers in base two. This function can return a floating point value when
passed two integers.
.. cfunction:: PyObject* PyNumber_Remainder(PyObject *o1, PyObject *o2)
Returns the remainder of dividing *o1* by *o2*, or *NULL* on failure. This is
the equivalent of the Python expression ``o1 % o2``.
.. cfunction:: PyObject* PyNumber_Divmod(PyObject *o1, PyObject *o2)
.. index:: builtin: divmod
See the built-in function :func:`divmod`. Returns *NULL* on failure. This is
the equivalent of the Python expression ``divmod(o1, o2)``.
.. cfunction:: PyObject* PyNumber_Power(PyObject *o1, PyObject *o2, PyObject *o3)
.. index:: builtin: pow
See the built-in function :func:`pow`. Returns *NULL* on failure. This is the
equivalent of the Python expression ``pow(o1, o2, o3)``, where *o3* is optional.
If *o3* is to be ignored, pass :cdata:`Py_None` in its place (passing *NULL* for
*o3* would cause an illegal memory access).
.. cfunction:: PyObject* PyNumber_Negative(PyObject *o)
Returns the negation of *o* on success, or *NULL* on failure. This is the
equivalent of the Python expression ``-o``.
.. cfunction:: PyObject* PyNumber_Positive(PyObject *o)
Returns *o* on success, or *NULL* on failure. This is the equivalent of the
Python expression ``+o``.
.. cfunction:: PyObject* PyNumber_Absolute(PyObject *o)
.. index:: builtin: abs
Returns the absolute value of *o*, or *NULL* on failure. This is the equivalent
of the Python expression ``abs(o)``.
.. cfunction:: PyObject* PyNumber_Invert(PyObject *o)
Returns the bitwise negation of *o* on success, or *NULL* on failure. This is
the equivalent of the Python expression ``~o``.
.. cfunction:: PyObject* PyNumber_Lshift(PyObject *o1, PyObject *o2)
Returns the result of left shifting *o1* by *o2* on success, or *NULL* on
failure. This is the equivalent of the Python expression ``o1 << o2``.
.. cfunction:: PyObject* PyNumber_Rshift(PyObject *o1, PyObject *o2)
Returns the result of right shifting *o1* by *o2* on success, or *NULL* on
failure. This is the equivalent of the Python expression ``o1 >> o2``.
.. cfunction:: PyObject* PyNumber_And(PyObject *o1, PyObject *o2)
Returns the "bitwise and" of *o1* and *o2* on success and *NULL* on failure.
This is the equivalent of the Python expression ``o1 & o2``.
.. cfunction:: PyObject* PyNumber_Xor(PyObject *o1, PyObject *o2)
Returns the "bitwise exclusive or" of *o1* by *o2* on success, or *NULL* on
failure. This is the equivalent of the Python expression ``o1 ^ o2``.
.. cfunction:: PyObject* PyNumber_Or(PyObject *o1, PyObject *o2)
Returns the "bitwise or" of *o1* and *o2* on success, or *NULL* on failure.
This is the equivalent of the Python expression ``o1 | o2``.
.. cfunction:: PyObject* PyNumber_InPlaceAdd(PyObject *o1, PyObject *o2)
Returns the result of adding *o1* and *o2*, or *NULL* on failure. The operation
is done *in-place* when *o1* supports it. This is the equivalent of the Python
statement ``o1 += o2``.
.. cfunction:: PyObject* PyNumber_InPlaceSubtract(PyObject *o1, PyObject *o2)
Returns the result of subtracting *o2* from *o1*, or *NULL* on failure. The
operation is done *in-place* when *o1* supports it. This is the equivalent of
the Python statement ``o1 -= o2``.
.. cfunction:: PyObject* PyNumber_InPlaceMultiply(PyObject *o1, PyObject *o2)
Returns the result of multiplying *o1* and *o2*, or *NULL* on failure. The
operation is done *in-place* when *o1* supports it. This is the equivalent of
the Python statement ``o1 *= o2``.
.. cfunction:: PyObject* PyNumber_InPlaceDivide(PyObject *o1, PyObject *o2)
Returns the result of dividing *o1* by *o2*, or *NULL* on failure. The
operation is done *in-place* when *o1* supports it. This is the equivalent of
the Python statement ``o1 /= o2``.
.. cfunction:: PyObject* PyNumber_InPlaceFloorDivide(PyObject *o1, PyObject *o2)
Returns the mathematical floor of dividing *o1* by *o2*, or *NULL* on failure.
The operation is done *in-place* when *o1* supports it. This is the equivalent
of the Python statement ``o1 //= o2``.
.. cfunction:: PyObject* PyNumber_InPlaceTrueDivide(PyObject *o1, PyObject *o2)
Return a reasonable approximation for the mathematical value of *o1* divided by
*o2*, or *NULL* on failure. The return value is "approximate" because binary
floating point numbers are approximate; it is not possible to represent all real
numbers in base two. This function can return a floating point value when
passed two integers. The operation is done *in-place* when *o1* supports it.
.. cfunction:: PyObject* PyNumber_InPlaceRemainder(PyObject *o1, PyObject *o2)
Returns the remainder of dividing *o1* by *o2*, or *NULL* on failure. The
operation is done *in-place* when *o1* supports it. This is the equivalent of
the Python statement ``o1 %= o2``.
.. cfunction:: PyObject* PyNumber_InPlacePower(PyObject *o1, PyObject *o2, PyObject *o3)
.. index:: builtin: pow
See the built-in function :func:`pow`. Returns *NULL* on failure. The operation
is done *in-place* when *o1* supports it. This is the equivalent of the Python
statement ``o1 **= o2`` when o3 is :cdata:`Py_None`, or an in-place variant of
``pow(o1, o2, o3)`` otherwise. If *o3* is to be ignored, pass :cdata:`Py_None`
in its place (passing *NULL* for *o3* would cause an illegal memory access).
.. cfunction:: PyObject* PyNumber_InPlaceLshift(PyObject *o1, PyObject *o2)
Returns the result of left shifting *o1* by *o2* on success, or *NULL* on
failure. The operation is done *in-place* when *o1* supports it. This is the
equivalent of the Python statement ``o1 <<= o2``.
.. cfunction:: PyObject* PyNumber_InPlaceRshift(PyObject *o1, PyObject *o2)
Returns the result of right shifting *o1* by *o2* on success, or *NULL* on
failure. The operation is done *in-place* when *o1* supports it. This is the
equivalent of the Python statement ``o1 >>= o2``.
.. cfunction:: PyObject* PyNumber_InPlaceAnd(PyObject *o1, PyObject *o2)
Returns the "bitwise and" of *o1* and *o2* on success and *NULL* on failure. The
operation is done *in-place* when *o1* supports it. This is the equivalent of
the Python statement ``o1 &= o2``.
.. cfunction:: PyObject* PyNumber_InPlaceXor(PyObject *o1, PyObject *o2)
Returns the "bitwise exclusive or" of *o1* by *o2* on success, or *NULL* on
failure. The operation is done *in-place* when *o1* supports it. This is the
equivalent of the Python statement ``o1 ^= o2``.
.. cfunction:: PyObject* PyNumber_InPlaceOr(PyObject *o1, PyObject *o2)
Returns the "bitwise or" of *o1* and *o2* on success, or *NULL* on failure. The
operation is done *in-place* when *o1* supports it. This is the equivalent of
the Python statement ``o1 |= o2``.
.. cfunction:: PyObject* PyNumber_Int(PyObject *o)
.. index:: builtin: int
Returns the *o* converted to an integer object on success, or *NULL* on failure.
If the argument is outside the integer range a long object will be returned
instead. This is the equivalent of the Python expression ``int(o)``.
.. cfunction:: PyObject* PyNumber_Long(PyObject *o)
.. index:: builtin: long
Returns the *o* converted to an integer object on success, or *NULL* on
failure. This is the equivalent of the Python expression ``long(o)``.
.. cfunction:: PyObject* PyNumber_Float(PyObject *o)
.. index:: builtin: float
Returns the *o* converted to a float object on success, or *NULL* on failure.
This is the equivalent of the Python expression ``float(o)``.
.. cfunction:: PyObject* PyNumber_Index(PyObject *o)
Returns the *o* converted to a Python int or long on success or *NULL* with a
TypeError exception raised on failure.
.. cfunction:: Py_ssize_t PyNumber_AsSsize_t(PyObject *o, PyObject *exc)
Returns *o* converted to a Py_ssize_t value if *o* can be interpreted as an
integer. If *o* can be converted to a Python int or long but the attempt to
convert to a Py_ssize_t value would raise an :exc:`OverflowError`, then the
*exc* argument is the type of exception that will be raised (usually
:exc:`IndexError` or :exc:`OverflowError`). If *exc* is *NULL*, then the
exception is cleared and the value is clipped to *PY_SSIZE_T_MIN* for a negative
integer or *PY_SSIZE_T_MAX* for a positive integer.
.. cfunction:: int PyIndex_Check(PyObject *o)
Returns True if *o* is an index integer (has the nb_index slot of the
tp_as_number structure filled in).

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.. highlightlang:: c
.. _abstract-buffer:
Buffer Protocol
===============
.. cfunction:: int PyObject_AsCharBuffer(PyObject *obj, const char **buffer, Py_ssize_t *buffer_len)
Returns a pointer to a read-only memory location useable as character- based
input. The *obj* argument must support the single-segment character buffer
interface. On success, returns ``0``, sets *buffer* to the memory location and
*buffer_len* to the buffer length. Returns ``-1`` and sets a :exc:`TypeError`
on error.
.. cfunction:: int PyObject_AsReadBuffer(PyObject *obj, const void **buffer, Py_ssize_t *buffer_len)
Returns a pointer to a read-only memory location containing arbitrary data. The
*obj* argument must support the single-segment readable buffer interface. On
success, returns ``0``, sets *buffer* to the memory location and *buffer_len* to
the buffer length. Returns ``-1`` and sets a :exc:`TypeError` on error.
.. cfunction:: int PyObject_CheckReadBuffer(PyObject *o)
Returns ``1`` if *o* supports the single-segment readable buffer interface.
Otherwise returns ``0``.
.. cfunction:: int PyObject_AsWriteBuffer(PyObject *obj, void **buffer, Py_ssize_t *buffer_len)
Returns a pointer to a writable memory location. The *obj* argument must
support the single-segment, character buffer interface. On success, returns
``0``, sets *buffer* to the memory location and *buffer_len* to the buffer
length. Returns ``-1`` and sets a :exc:`TypeError` on error.

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.. highlightlang:: c
.. _object:
Object Protocol
===============
.. cfunction:: int PyObject_Print(PyObject *o, FILE *fp, int flags)
Print an object *o*, on file *fp*. Returns ``-1`` on error. The flags argument
is used to enable certain printing options. The only option currently supported
is :const:`Py_PRINT_RAW`; if given, the :func:`str` of the object is written
instead of the :func:`repr`.
.. cfunction:: int PyObject_HasAttr(PyObject *o, PyObject *attr_name)
Returns ``1`` if *o* has the attribute *attr_name*, and ``0`` otherwise. This
is equivalent to the Python expression ``hasattr(o, attr_name)``. This function
always succeeds.
.. cfunction:: int PyObject_HasAttrString(PyObject *o, const char *attr_name)
Returns ``1`` if *o* has the attribute *attr_name*, and ``0`` otherwise. This
is equivalent to the Python expression ``hasattr(o, attr_name)``. This function
always succeeds.
.. cfunction:: PyObject* PyObject_GetAttr(PyObject *o, PyObject *attr_name)
Retrieve an attribute named *attr_name* from object *o*. Returns the attribute
value on success, or *NULL* on failure. This is the equivalent of the Python
expression ``o.attr_name``.
.. cfunction:: PyObject* PyObject_GetAttrString(PyObject *o, const char *attr_name)
Retrieve an attribute named *attr_name* from object *o*. Returns the attribute
value on success, or *NULL* on failure. This is the equivalent of the Python
expression ``o.attr_name``.
.. cfunction:: int PyObject_SetAttr(PyObject *o, PyObject *attr_name, PyObject *v)
Set the value of the attribute named *attr_name*, for object *o*, to the value
*v*. Returns ``-1`` on failure. This is the equivalent of the Python statement
``o.attr_name = v``.
.. cfunction:: int PyObject_SetAttrString(PyObject *o, const char *attr_name, PyObject *v)
Set the value of the attribute named *attr_name*, for object *o*, to the value
*v*. Returns ``-1`` on failure. This is the equivalent of the Python statement
``o.attr_name = v``.
.. cfunction:: int PyObject_DelAttr(PyObject *o, PyObject *attr_name)
Delete attribute named *attr_name*, for object *o*. Returns ``-1`` on failure.
This is the equivalent of the Python statement ``del o.attr_name``.
.. cfunction:: int PyObject_DelAttrString(PyObject *o, const char *attr_name)
Delete attribute named *attr_name*, for object *o*. Returns ``-1`` on failure.
This is the equivalent of the Python statement ``del o.attr_name``.
.. cfunction:: PyObject* PyObject_RichCompare(PyObject *o1, PyObject *o2, int opid)
Compare the values of *o1* and *o2* using the operation specified by *opid*,
which must be one of :const:`Py_LT`, :const:`Py_LE`, :const:`Py_EQ`,
:const:`Py_NE`, :const:`Py_GT`, or :const:`Py_GE`, corresponding to ``<``,
``<=``, ``==``, ``!=``, ``>``, or ``>=`` respectively. This is the equivalent of
the Python expression ``o1 op o2``, where ``op`` is the operator corresponding
to *opid*. Returns the value of the comparison on success, or *NULL* on failure.
.. cfunction:: int PyObject_RichCompareBool(PyObject *o1, PyObject *o2, int opid)
Compare the values of *o1* and *o2* using the operation specified by *opid*,
which must be one of :const:`Py_LT`, :const:`Py_LE`, :const:`Py_EQ`,
:const:`Py_NE`, :const:`Py_GT`, or :const:`Py_GE`, corresponding to ``<``,
``<=``, ``==``, ``!=``, ``>``, or ``>=`` respectively. Returns ``-1`` on error,
``0`` if the result is false, ``1`` otherwise. This is the equivalent of the
Python expression ``o1 op o2``, where ``op`` is the operator corresponding to
*opid*.
.. cfunction:: int PyObject_Cmp(PyObject *o1, PyObject *o2, int *result)
.. index:: builtin: cmp
Compare the values of *o1* and *o2* using a routine provided by *o1*, if one
exists, otherwise with a routine provided by *o2*. The result of the comparison
is returned in *result*. Returns ``-1`` on failure. This is the equivalent of
the Python statement ``result = cmp(o1, o2)``.
.. cfunction:: int PyObject_Compare(PyObject *o1, PyObject *o2)
.. index:: builtin: cmp
Compare the values of *o1* and *o2* using a routine provided by *o1*, if one
exists, otherwise with a routine provided by *o2*. Returns the result of the
comparison on success. On error, the value returned is undefined; use
:cfunc:`PyErr_Occurred` to detect an error. This is equivalent to the Python
expression ``cmp(o1, o2)``.
.. cfunction:: PyObject* PyObject_Repr(PyObject *o)
.. index:: builtin: repr
Compute a string representation of object *o*. Returns the string
representation on success, *NULL* on failure. This is the equivalent of the
Python expression ``repr(o)``. Called by the :func:`repr` built-in function and
by reverse quotes.
.. cfunction:: PyObject* PyObject_Str(PyObject *o)
.. index:: builtin: str
Compute a string representation of object *o*. Returns the string
representation on success, *NULL* on failure. This is the equivalent of the
Python expression ``str(o)``. Called by the :func:`str` built-in function
and, therefore, by the :func:`print` function.
.. cfunction:: PyObject* PyObject_Unicode(PyObject *o)
.. index:: builtin: unicode
Compute a Unicode string representation of object *o*. Returns the Unicode
string representation on success, *NULL* on failure. This is the equivalent of
the Python expression ``unicode(o)``. Called by the :func:`unicode` built-in
function.
.. cfunction:: int PyObject_IsInstance(PyObject *inst, PyObject *cls)
Returns ``1`` if *inst* is an instance of the class *cls* or a subclass of
*cls*, or ``0`` if not. On error, returns ``-1`` and sets an exception. If
*cls* is a type object rather than a class object, :cfunc:`PyObject_IsInstance`
returns ``1`` if *inst* is of type *cls*. If *cls* is a tuple, the check will
be done against every entry in *cls*. The result will be ``1`` when at least one
of the checks returns ``1``, otherwise it will be ``0``. If *inst* is not a
class instance and *cls* is neither a type object, nor a class object, nor a
tuple, *inst* must have a :attr:`__class__` attribute --- the class relationship
of the value of that attribute with *cls* will be used to determine the result
of this function.
Subclass determination is done in a fairly straightforward way, but includes a
wrinkle that implementors of extensions to the class system may want to be aware
of. If :class:`A` and :class:`B` are class objects, :class:`B` is a subclass of
:class:`A` if it inherits from :class:`A` either directly or indirectly. If
either is not a class object, a more general mechanism is used to determine the
class relationship of the two objects. When testing if *B* is a subclass of
*A*, if *A* is *B*, :cfunc:`PyObject_IsSubclass` returns true. If *A* and *B*
are different objects, *B*'s :attr:`__bases__` attribute is searched in a
depth-first fashion for *A* --- the presence of the :attr:`__bases__` attribute
is considered sufficient for this determination.
.. cfunction:: int PyObject_IsSubclass(PyObject *derived, PyObject *cls)
Returns ``1`` if the class *derived* is identical to or derived from the class
*cls*, otherwise returns ``0``. In case of an error, returns ``-1``. If *cls*
is a tuple, the check will be done against every entry in *cls*. The result will
be ``1`` when at least one of the checks returns ``1``, otherwise it will be
``0``. If either *derived* or *cls* is not an actual class object (or tuple),
this function uses the generic algorithm described above.
.. cfunction:: int PyCallable_Check(PyObject *o)
Determine if the object *o* is callable. Return ``1`` if the object is callable
and ``0`` otherwise. This function always succeeds.
.. cfunction:: PyObject* PyObject_Call(PyObject *callable_object, PyObject *args, PyObject *kw)
Call a callable Python object *callable_object*, with arguments given by the
tuple *args*, and named arguments given by the dictionary *kw*. If no named
arguments are needed, *kw* may be *NULL*. *args* must not be *NULL*, use an
empty tuple if no arguments are needed. Returns the result of the call on
success, or *NULL* on failure. This is the equivalent of the Python expression
``callable_object(*args, **kw)``.
.. cfunction:: PyObject* PyObject_CallObject(PyObject *callable_object, PyObject *args)
Call a callable Python object *callable_object*, with arguments given by the
tuple *args*. If no arguments are needed, then *args* may be *NULL*. Returns
the result of the call on success, or *NULL* on failure. This is the equivalent
of the Python expression ``callable_object(*args)``.
.. cfunction:: PyObject* PyObject_CallFunction(PyObject *callable, char *format, ...)
Call a callable Python object *callable*, with a variable number of C arguments.
The C arguments are described using a :cfunc:`Py_BuildValue` style format
string. The format may be *NULL*, indicating that no arguments are provided.
Returns the result of the call on success, or *NULL* on failure. This is the
equivalent of the Python expression ``callable(*args)``. Note that if you only
pass :ctype:`PyObject \*` args, :cfunc:`PyObject_CallFunctionObjArgs` is a
faster alternative.
.. cfunction:: PyObject* PyObject_CallMethod(PyObject *o, char *method, char *format, ...)
Call the method named *method* of object *o* with a variable number of C
arguments. The C arguments are described by a :cfunc:`Py_BuildValue` format
string that should produce a tuple. The format may be *NULL*, indicating that
no arguments are provided. Returns the result of the call on success, or *NULL*
on failure. This is the equivalent of the Python expression ``o.method(args)``.
Note that if you only pass :ctype:`PyObject \*` args,
:cfunc:`PyObject_CallMethodObjArgs` is a faster alternative.
.. cfunction:: PyObject* PyObject_CallFunctionObjArgs(PyObject *callable, ..., NULL)
Call a callable Python object *callable*, with a variable number of
:ctype:`PyObject\*` arguments. The arguments are provided as a variable number
of parameters followed by *NULL*. Returns the result of the call on success, or
*NULL* on failure.
.. cfunction:: PyObject* PyObject_CallMethodObjArgs(PyObject *o, PyObject *name, ..., NULL)
Calls a method of the object *o*, where the name of the method is given as a
Python string object in *name*. It is called with a variable number of
:ctype:`PyObject\*` arguments. The arguments are provided as a variable number
of parameters followed by *NULL*. Returns the result of the call on success, or
*NULL* on failure.
.. cfunction:: long PyObject_Hash(PyObject *o)
.. index:: builtin: hash
Compute and return the hash value of an object *o*. On failure, return ``-1``.
This is the equivalent of the Python expression ``hash(o)``.
.. cfunction:: int PyObject_IsTrue(PyObject *o)
Returns ``1`` if the object *o* is considered to be true, and ``0`` otherwise.
This is equivalent to the Python expression ``not not o``. On failure, return
``-1``.
.. cfunction:: int PyObject_Not(PyObject *o)
Returns ``0`` if the object *o* is considered to be true, and ``1`` otherwise.
This is equivalent to the Python expression ``not o``. On failure, return
``-1``.
.. cfunction:: PyObject* PyObject_Type(PyObject *o)
.. index:: builtin: type
When *o* is non-*NULL*, returns a type object corresponding to the object type
of object *o*. On failure, raises :exc:`SystemError` and returns *NULL*. This
is equivalent to the Python expression ``type(o)``. This function increments the
reference count of the return value. There's really no reason to use this
function instead of the common expression ``o->ob_type``, which returns a
pointer of type :ctype:`PyTypeObject\*`, except when the incremented reference
count is needed.
.. cfunction:: int PyObject_TypeCheck(PyObject *o, PyTypeObject *type)
Return true if the object *o* is of type *type* or a subtype of *type*. Both
parameters must be non-*NULL*.
.. cfunction:: Py_ssize_t PyObject_Length(PyObject *o)
Py_ssize_t PyObject_Size(PyObject *o)
.. index:: builtin: len
Return the length of object *o*. If the object *o* provides either the sequence
and mapping protocols, the sequence length is returned. On error, ``-1`` is
returned. This is the equivalent to the Python expression ``len(o)``.
.. cfunction:: PyObject* PyObject_GetItem(PyObject *o, PyObject *key)
Return element of *o* corresponding to the object *key* or *NULL* on failure.
This is the equivalent of the Python expression ``o[key]``.
.. cfunction:: int PyObject_SetItem(PyObject *o, PyObject *key, PyObject *v)
Map the object *key* to the value *v*. Returns ``-1`` on failure. This is the
equivalent of the Python statement ``o[key] = v``.
.. cfunction:: int PyObject_DelItem(PyObject *o, PyObject *key)
Delete the mapping for *key* from *o*. Returns ``-1`` on failure. This is the
equivalent of the Python statement ``del o[key]``.
.. cfunction:: PyObject* PyObject_Dir(PyObject *o)
This is equivalent to the Python expression ``dir(o)``, returning a (possibly
empty) list of strings appropriate for the object argument, or *NULL* if there
was an error. If the argument is *NULL*, this is like the Python ``dir()``,
returning the names of the current locals; in this case, if no execution frame
is active then *NULL* is returned but :cfunc:`PyErr_Occurred` will return false.
.. cfunction:: PyObject* PyObject_GetIter(PyObject *o)
This is equivalent to the Python expression ``iter(o)``. It returns a new
iterator for the object argument, or the object itself if the object is already
an iterator. Raises :exc:`TypeError` and returns *NULL* if the object cannot be
iterated.

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.. highlightlang:: c
.. _newtypes:
*****************************
Object Implementation Support
*****************************
This chapter describes the functions, types, and macros used when defining new
object types.
.. toctree::
allocation.rst
structures.rst
typeobj.rst
gcsupport.rst

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.. highlightlang:: c
.. _reflection:
Reflection
==========
.. cfunction:: PyObject* PyEval_GetBuiltins()
Return a dictionary of the builtins in the current execution frame,
or the interpreter of the thread state if no frame is currently executing.
.. cfunction:: PyObject* PyEval_GetLocals()
Return a dictionary of the local variables in the current execution frame,
or *NULL* if no frame is currently executing.
.. cfunction:: PyObject* PyEval_GetGlobals()
Return a dictionary of the global variables in the current execution frame,
or *NULL* if no frame is currently executing.
.. cfunction:: PyFrameObject* PyEval_GetFrame()
Return the current thread state's frame, which is *NULL* if no frame is
currently executing.
.. cfunction:: int PyEval_GetRestricted()
If there is a current frame and it is executing in restricted mode, return true,
otherwise false.
.. cfunction:: const char* PyEval_GetFuncName(PyObject *func)
Return the name of *func* if it is a function, class or instance object, else the
name of *func*\s type.
.. cfunction:: const char* PyEval_GetFuncDesc(PyObject *func)
Return a description string, depending on the type of *func*.
Return values include "()" for functions and methods, " constructor",
" instance", and " object". Concatenated with the result of
:cfunc:`PyEval_GetFuncName`, the result will be a description of
*func*.

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.. highlightlang:: c
.. _sequence:
Sequence Protocol
=================
.. cfunction:: int PySequence_Check(PyObject *o)
Return ``1`` if the object provides sequence protocol, and ``0`` otherwise.
This function always succeeds.
.. cfunction:: Py_ssize_t PySequence_Size(PyObject *o)
.. index:: builtin: len
Returns the number of objects in sequence *o* on success, and ``-1`` on failure.
For objects that do not provide sequence protocol, this is equivalent to the
Python expression ``len(o)``.
.. cfunction:: Py_ssize_t PySequence_Length(PyObject *o)
Alternate name for :cfunc:`PySequence_Size`.
.. cfunction:: PyObject* PySequence_Concat(PyObject *o1, PyObject *o2)
Return the concatenation of *o1* and *o2* on success, and *NULL* on failure.
This is the equivalent of the Python expression ``o1 + o2``.
.. cfunction:: PyObject* PySequence_Repeat(PyObject *o, Py_ssize_t count)
Return the result of repeating sequence object *o* *count* times, or *NULL* on
failure. This is the equivalent of the Python expression ``o * count``.
.. cfunction:: PyObject* PySequence_InPlaceConcat(PyObject *o1, PyObject *o2)
Return the concatenation of *o1* and *o2* on success, and *NULL* on failure.
The operation is done *in-place* when *o1* supports it. This is the equivalent
of the Python expression ``o1 += o2``.
.. cfunction:: PyObject* PySequence_InPlaceRepeat(PyObject *o, Py_ssize_t count)
Return the result of repeating sequence object *o* *count* times, or *NULL* on
failure. The operation is done *in-place* when *o* supports it. This is the
equivalent of the Python expression ``o *= count``.
.. cfunction:: PyObject* PySequence_GetItem(PyObject *o, Py_ssize_t i)
Return the *i*th element of *o*, or *NULL* on failure. This is the equivalent of
the Python expression ``o[i]``.
.. cfunction:: PyObject* PySequence_GetSlice(PyObject *o, Py_ssize_t i1, Py_ssize_t i2)
Return the slice of sequence object *o* between *i1* and *i2*, or *NULL* on
failure. This is the equivalent of the Python expression ``o[i1:i2]``.
.. cfunction:: int PySequence_SetItem(PyObject *o, Py_ssize_t i, PyObject *v)
Assign object *v* to the *i*th element of *o*. Returns ``-1`` on failure. This
is the equivalent of the Python statement ``o[i] = v``. This function *does
not* steal a reference to *v*.
.. cfunction:: int PySequence_DelItem(PyObject *o, Py_ssize_t i)
Delete the *i*th element of object *o*. Returns ``-1`` on failure. This is the
equivalent of the Python statement ``del o[i]``.
.. cfunction:: int PySequence_SetSlice(PyObject *o, Py_ssize_t i1, Py_ssize_t i2, PyObject *v)
Assign the sequence object *v* to the slice in sequence object *o* from *i1* to
*i2*. This is the equivalent of the Python statement ``o[i1:i2] = v``.
.. cfunction:: int PySequence_DelSlice(PyObject *o, Py_ssize_t i1, Py_ssize_t i2)
Delete the slice in sequence object *o* from *i1* to *i2*. Returns ``-1`` on
failure. This is the equivalent of the Python statement ``del o[i1:i2]``.
.. cfunction:: Py_ssize_t PySequence_Count(PyObject *o, PyObject *value)
Return the number of occurrences of *value* in *o*, that is, return the number
of keys for which ``o[key] == value``. On failure, return ``-1``. This is
equivalent to the Python expression ``o.count(value)``.
.. cfunction:: int PySequence_Contains(PyObject *o, PyObject *value)
Determine if *o* contains *value*. If an item in *o* is equal to *value*,
return ``1``, otherwise return ``0``. On error, return ``-1``. This is
equivalent to the Python expression ``value in o``.
.. cfunction:: Py_ssize_t PySequence_Index(PyObject *o, PyObject *value)
Return the first index *i* for which ``o[i] == value``. On error, return
``-1``. This is equivalent to the Python expression ``o.index(value)``.
.. cfunction:: PyObject* PySequence_List(PyObject *o)
Return a list object with the same contents as the arbitrary sequence *o*. The
returned list is guaranteed to be new.
.. cfunction:: PyObject* PySequence_Tuple(PyObject *o)
.. index:: builtin: tuple
Return a tuple object with the same contents as the arbitrary sequence *o* or
*NULL* on failure. If *o* is a tuple, a new reference will be returned,
otherwise a tuple will be constructed with the appropriate contents. This is
equivalent to the Python expression ``tuple(o)``.
.. cfunction:: PyObject* PySequence_Fast(PyObject *o, const char *m)
Returns the sequence *o* as a tuple, unless it is already a tuple or list, in
which case *o* is returned. Use :cfunc:`PySequence_Fast_GET_ITEM` to access the
members of the result. Returns *NULL* on failure. If the object is not a
sequence, raises :exc:`TypeError` with *m* as the message text.
.. cfunction:: PyObject* PySequence_Fast_GET_ITEM(PyObject *o, Py_ssize_t i)
Return the *i*th element of *o*, assuming that *o* was returned by
:cfunc:`PySequence_Fast`, *o* is not *NULL*, and that *i* is within bounds.
.. cfunction:: PyObject** PySequence_Fast_ITEMS(PyObject *o)
Return the underlying array of PyObject pointers. Assumes that *o* was returned
by :cfunc:`PySequence_Fast` and *o* is not *NULL*.
.. cfunction:: PyObject* PySequence_ITEM(PyObject *o, Py_ssize_t i)
Return the *i*th element of *o* or *NULL* on failure. Macro form of
:cfunc:`PySequence_GetItem` but without checking that
:cfunc:`PySequence_Check(o)` is true and without adjustment for negative
indices.
.. cfunction:: Py_ssize_t PySequence_Fast_GET_SIZE(PyObject *o)
Returns the length of *o*, assuming that *o* was returned by
:cfunc:`PySequence_Fast` and that *o* is not *NULL*. The size can also be
gotten by calling :cfunc:`PySequence_Size` on *o*, but
:cfunc:`PySequence_Fast_GET_SIZE` is faster because it can assume *o* is a list
or tuple.

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.. highlightlang:: c
.. _setobjects:
Set Objects
-----------
.. sectionauthor:: Raymond D. Hettinger <python@rcn.com>
.. index::
object: set
object: frozenset
This section details the public API for :class:`set` and :class:`frozenset`
objects. Any functionality not listed below is best accessed using the either
the abstract object protocol (including :cfunc:`PyObject_CallMethod`,
:cfunc:`PyObject_RichCompareBool`, :cfunc:`PyObject_Hash`,
:cfunc:`PyObject_Repr`, :cfunc:`PyObject_IsTrue`, :cfunc:`PyObject_Print`, and
:cfunc:`PyObject_GetIter`) or the abstract number protocol (including
:cfunc:`PyNumber_And`, :cfunc:`PyNumber_Subtract`, :cfunc:`PyNumber_Or`,
:cfunc:`PyNumber_Xor`, :cfunc:`PyNumber_InPlaceAnd`,
:cfunc:`PyNumber_InPlaceSubtract`, :cfunc:`PyNumber_InPlaceOr`, and
:cfunc:`PyNumber_InPlaceXor`).
.. ctype:: PySetObject
This subtype of :ctype:`PyObject` is used to hold the internal data for both
:class:`set` and :class:`frozenset` objects. It is like a :ctype:`PyDictObject`
in that it is a fixed size for small sets (much like tuple storage) and will
point to a separate, variable sized block of memory for medium and large sized
sets (much like list storage). None of the fields of this structure should be
considered public and are subject to change. All access should be done through
the documented API rather than by manipulating the values in the structure.
.. cvar:: PyTypeObject PySet_Type
This is an instance of :ctype:`PyTypeObject` representing the Python
:class:`set` type.
.. cvar:: PyTypeObject PyFrozenSet_Type
This is an instance of :ctype:`PyTypeObject` representing the Python
:class:`frozenset` type.
The following type check macros work on pointers to any Python object. Likewise,
the constructor functions work with any iterable Python object.
.. cfunction:: int PyAnySet_Check(PyObject *p)
Return true if *p* is a :class:`set` object, a :class:`frozenset` object, or an
instance of a subtype.
.. cfunction:: int PyAnySet_CheckExact(PyObject *p)
Return true if *p* is a :class:`set` object or a :class:`frozenset` object but
not an instance of a subtype.
.. cfunction:: int PyFrozenSet_CheckExact(PyObject *p)
Return true if *p* is a :class:`frozenset` object but not an instance of a
subtype.
.. cfunction:: PyObject* PySet_New(PyObject *iterable)
Return a new :class:`set` containing objects returned by the *iterable*. The
*iterable* may be *NULL* to create a new empty set. Return the new set on
success or *NULL* on failure. Raise :exc:`TypeError` if *iterable* is not
actually iterable. The constructor is also useful for copying a set
(``c=set(s)``).
.. cfunction:: PyObject* PyFrozenSet_New(PyObject *iterable)
Return a new :class:`frozenset` containing objects returned by the *iterable*.
The *iterable* may be *NULL* to create a new empty frozenset. Return the new
set on success or *NULL* on failure. Raise :exc:`TypeError` if *iterable* is
not actually iterable.
The following functions and macros are available for instances of :class:`set`
or :class:`frozenset` or instances of their subtypes.
.. cfunction:: Py_ssize_t PySet_Size(PyObject *anyset)
.. index:: builtin: len
Return the length of a :class:`set` or :class:`frozenset` object. Equivalent to
``len(anyset)``. Raises a :exc:`PyExc_SystemError` if *anyset* is not a
:class:`set`, :class:`frozenset`, or an instance of a subtype.
.. cfunction:: Py_ssize_t PySet_GET_SIZE(PyObject *anyset)
Macro form of :cfunc:`PySet_Size` without error checking.
.. cfunction:: int PySet_Contains(PyObject *anyset, PyObject *key)
Return 1 if found, 0 if not found, and -1 if an error is encountered. Unlike
the Python :meth:`__contains__` method, this function does not automatically
convert unhashable sets into temporary frozensets. Raise a :exc:`TypeError` if
the *key* is unhashable. Raise :exc:`PyExc_SystemError` if *anyset* is not a
:class:`set`, :class:`frozenset`, or an instance of a subtype.
The following functions are available for instances of :class:`set` or its
subtypes but not for instances of :class:`frozenset` or its subtypes.
.. cfunction:: int PySet_Add(PyObject *set, PyObject *key)
Add *key* to a :class:`set` instance. Does not apply to :class:`frozenset`
instances. Return 0 on success or -1 on failure. Raise a :exc:`TypeError` if
the *key* is unhashable. Raise a :exc:`MemoryError` if there is no room to grow.
Raise a :exc:`SystemError` if *set* is an not an instance of :class:`set` or its
subtype.
.. cfunction:: int PySet_Discard(PyObject *set, PyObject *key)
Return 1 if found and removed, 0 if not found (no action taken), and -1 if an
error is encountered. Does not raise :exc:`KeyError` for missing keys. Raise a
:exc:`TypeError` if the *key* is unhashable. Unlike the Python :meth:`discard`
method, this function does not automatically convert unhashable sets into
temporary frozensets. Raise :exc:`PyExc_SystemError` if *set* is an not an
instance of :class:`set` or its subtype.
.. cfunction:: PyObject* PySet_Pop(PyObject *set)
Return a new reference to an arbitrary object in the *set*, and removes the
object from the *set*. Return *NULL* on failure. Raise :exc:`KeyError` if the
set is empty. Raise a :exc:`SystemError` if *set* is an not an instance of
:class:`set` or its subtype.
.. cfunction:: int PySet_Clear(PyObject *set)
Empty an existing set of all elements.

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.. highlightlang:: c
.. _slice-objects:
Slice Objects
-------------
.. cvar:: PyTypeObject PySlice_Type
.. index:: single: SliceType (in module types)
The type object for slice objects. This is the same as ``slice`` and
``types.SliceType``.
.. cfunction:: int PySlice_Check(PyObject *ob)
Return true if *ob* is a slice object; *ob* must not be *NULL*.
.. cfunction:: PyObject* PySlice_New(PyObject *start, PyObject *stop, PyObject *step)
Return a new slice object with the given values. The *start*, *stop*, and
*step* parameters are used as the values of the slice object attributes of the
same names. Any of the values may be *NULL*, in which case the ``None`` will be
used for the corresponding attribute. Return *NULL* if the new object could not
be allocated.
.. cfunction:: int PySlice_GetIndices(PySliceObject *slice, Py_ssize_t length, Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step)
Retrieve the start, stop and step indices from the slice object *slice*,
assuming a sequence of length *length*. Treats indices greater than *length* as
errors.
Returns 0 on success and -1 on error with no exception set (unless one of the
indices was not :const:`None` and failed to be converted to an integer, in which
case -1 is returned with an exception set).
You probably do not want to use this function. If you want to use slice objects
in versions of Python prior to 2.3, you would probably do well to incorporate
the source of :cfunc:`PySlice_GetIndicesEx`, suitably renamed, in the source of
your extension.
.. cfunction:: int PySlice_GetIndicesEx(PySliceObject *slice, Py_ssize_t length, Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step, Py_ssize_t *slicelength)
Usable replacement for :cfunc:`PySlice_GetIndices`. Retrieve the start, stop,
and step indices from the slice object *slice* assuming a sequence of length
*length*, and store the length of the slice in *slicelength*. Out of bounds
indices are clipped in a manner consistent with the handling of normal slices.
Returns 0 on success and -1 on error with exception set.

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.. highlightlang:: c
.. _stringobjects:
String Objects
--------------
These functions raise :exc:`TypeError` when expecting a string parameter and are
called with a non-string parameter.
.. index:: object: string
.. ctype:: PyStringObject
This subtype of :ctype:`PyObject` represents a Python string object.
.. cvar:: PyTypeObject PyString_Type
.. index:: single: StringType (in module types)
This instance of :ctype:`PyTypeObject` represents the Python string type; it is
the same object as ``str`` and ``types.StringType`` in the Python layer. .
.. cfunction:: int PyString_Check(PyObject *o)
Return true if the object *o* is a string object or an instance of a subtype of
the string type.
.. cfunction:: int PyString_CheckExact(PyObject *o)
Return true if the object *o* is a string object, but not an instance of a
subtype of the string type.
.. cfunction:: PyObject* PyString_FromString(const char *v)
Return a new string object with a copy of the string *v* as value on success,
and *NULL* on failure. The parameter *v* must not be *NULL*; it will not be
checked.
.. cfunction:: PyObject* PyString_FromStringAndSize(const char *v, Py_ssize_t len)
Return a new string object with a copy of the string *v* as value and length
*len* on success, and *NULL* on failure. If *v* is *NULL*, the contents of the
string are uninitialized.
.. cfunction:: PyObject* PyString_FromFormat(const char *format, ...)
Take a C :cfunc:`printf`\ -style *format* string and a variable number of
arguments, calculate the size of the resulting Python string and return a string
with the values formatted into it. The variable arguments must be C types and
must correspond exactly to the format characters in the *format* string. The
following format characters are allowed:
.. % XXX: This should be exactly the same as the table in PyErr_Format.
.. % One should just refer to the other.
.. % XXX: The descriptions for %zd and %zu are wrong, but the truth is complicated
.. % because not all compilers support the %z width modifier -- we fake it
.. % when necessary via interpolating PY_FORMAT_SIZE_T.
.. % %u, %lu, %zu should have "new in Python 2.5" blurbs.
+-------------------+---------------+--------------------------------+
| Format Characters | Type | Comment |
+===================+===============+================================+
| :attr:`%%` | *n/a* | The literal % character. |
+-------------------+---------------+--------------------------------+
| :attr:`%c` | int | A single character, |
| | | represented as an C int. |
+-------------------+---------------+--------------------------------+
| :attr:`%d` | int | Exactly equivalent to |
| | | ``printf("%d")``. |
+-------------------+---------------+--------------------------------+
| :attr:`%u` | unsigned int | Exactly equivalent to |
| | | ``printf("%u")``. |
+-------------------+---------------+--------------------------------+
| :attr:`%ld` | long | Exactly equivalent to |
| | | ``printf("%ld")``. |
+-------------------+---------------+--------------------------------+
| :attr:`%lu` | unsigned long | Exactly equivalent to |
| | | ``printf("%lu")``. |
+-------------------+---------------+--------------------------------+
| :attr:`%zd` | Py_ssize_t | Exactly equivalent to |
| | | ``printf("%zd")``. |
+-------------------+---------------+--------------------------------+
| :attr:`%zu` | size_t | Exactly equivalent to |
| | | ``printf("%zu")``. |
+-------------------+---------------+--------------------------------+
| :attr:`%i` | int | Exactly equivalent to |
| | | ``printf("%i")``. |
+-------------------+---------------+--------------------------------+
| :attr:`%x` | int | Exactly equivalent to |
| | | ``printf("%x")``. |
+-------------------+---------------+--------------------------------+
| :attr:`%s` | char\* | A null-terminated C character |
| | | array. |
+-------------------+---------------+--------------------------------+
| :attr:`%p` | void\* | The hex representation of a C |
| | | pointer. Mostly equivalent to |
| | | ``printf("%p")`` except that |
| | | it is guaranteed to start with |
| | | the literal ``0x`` regardless |
| | | of what the platform's |
| | | ``printf`` yields. |
+-------------------+---------------+--------------------------------+
An unrecognized format character causes all the rest of the format string to be
copied as-is to the result string, and any extra arguments discarded.
.. cfunction:: PyObject* PyString_FromFormatV(const char *format, va_list vargs)
Identical to :func:`PyString_FromFormat` except that it takes exactly two
arguments.
.. cfunction:: Py_ssize_t PyString_Size(PyObject *string)
Return the length of the string in string object *string*.
.. cfunction:: Py_ssize_t PyString_GET_SIZE(PyObject *string)
Macro form of :cfunc:`PyString_Size` but without error checking.
.. cfunction:: char* PyString_AsString(PyObject *string)
Return a NUL-terminated representation of the contents of *string*. The pointer
refers to the internal buffer of *string*, not a copy. The data must not be
modified in any way, unless the string was just created using
``PyString_FromStringAndSize(NULL, size)``. It must not be deallocated. If
*string* is a Unicode object, this function computes the default encoding of
*string* and operates on that. If *string* is not a string object at all,
:cfunc:`PyString_AsString` returns *NULL* and raises :exc:`TypeError`.
.. cfunction:: char* PyString_AS_STRING(PyObject *string)
Macro form of :cfunc:`PyString_AsString` but without error checking. Only
string objects are supported; no Unicode objects should be passed.
.. cfunction:: int PyString_AsStringAndSize(PyObject *obj, char **buffer, Py_ssize_t *length)
Return a NUL-terminated representation of the contents of the object *obj*
through the output variables *buffer* and *length*.
The function accepts both string and Unicode objects as input. For Unicode
objects it returns the default encoded version of the object. If *length* is
*NULL*, the resulting buffer may not contain NUL characters; if it does, the
function returns ``-1`` and a :exc:`TypeError` is raised.
The buffer refers to an internal string buffer of *obj*, not a copy. The data
must not be modified in any way, unless the string was just created using
``PyString_FromStringAndSize(NULL, size)``. It must not be deallocated. If
*string* is a Unicode object, this function computes the default encoding of
*string* and operates on that. If *string* is not a string object at all,
:cfunc:`PyString_AsStringAndSize` returns ``-1`` and raises :exc:`TypeError`.
.. cfunction:: void PyString_Concat(PyObject **string, PyObject *newpart)
Create a new string object in *\*string* containing the contents of *newpart*
appended to *string*; the caller will own the new reference. The reference to
the old value of *string* will be stolen. If the new string cannot be created,
the old reference to *string* will still be discarded and the value of
*\*string* will be set to *NULL*; the appropriate exception will be set.
.. cfunction:: void PyString_ConcatAndDel(PyObject **string, PyObject *newpart)
Create a new string object in *\*string* containing the contents of *newpart*
appended to *string*. This version decrements the reference count of *newpart*.
.. cfunction:: int _PyString_Resize(PyObject **string, Py_ssize_t newsize)
A way to resize a string object even though it is "immutable". Only use this to
build up a brand new string object; don't use this if the string may already be
known in other parts of the code. It is an error to call this function if the
refcount on the input string object is not one. Pass the address of an existing
string object as an lvalue (it may be written into), and the new size desired.
On success, *\*string* holds the resized string object and ``0`` is returned;
the address in *\*string* may differ from its input value. If the reallocation
fails, the original string object at *\*string* is deallocated, *\*string* is
set to *NULL*, a memory exception is set, and ``-1`` is returned.
.. cfunction:: PyObject* PyString_Format(PyObject *format, PyObject *args)
Return a new string object from *format* and *args*. Analogous to ``format %
args``. The *args* argument must be a tuple.
.. cfunction:: void PyString_InternInPlace(PyObject **string)
Intern the argument *\*string* in place. The argument must be the address of a
pointer variable pointing to a Python string object. If there is an existing
interned string that is the same as *\*string*, it sets *\*string* to it
(decrementing the reference count of the old string object and incrementing the
reference count of the interned string object), otherwise it leaves *\*string*
alone and interns it (incrementing its reference count). (Clarification: even
though there is a lot of talk about reference counts, think of this function as
reference-count-neutral; you own the object after the call if and only if you
owned it before the call.)
.. cfunction:: PyObject* PyString_InternFromString(const char *v)
A combination of :cfunc:`PyString_FromString` and
:cfunc:`PyString_InternInPlace`, returning either a new string object that has
been interned, or a new ("owned") reference to an earlier interned string object
with the same value.
.. cfunction:: PyObject* PyString_Decode(const char *s, Py_ssize_t size, const char *encoding, const char *errors)
Create an object by decoding *size* bytes of the encoded buffer *s* using the
codec registered for *encoding*. *encoding* and *errors* have the same meaning
as the parameters of the same name in the :func:`unicode` built-in function.
The codec to be used is looked up using the Python codec registry. Return
*NULL* if an exception was raised by the codec.
.. cfunction:: PyObject* PyString_AsDecodedObject(PyObject *str, const char *encoding, const char *errors)
Decode a string object by passing it to the codec registered for *encoding* and
return the result as Python object. *encoding* and *errors* have the same
meaning as the parameters of the same name in the string :meth:`encode` method.
The codec to be used is looked up using the Python codec registry. Return *NULL*
if an exception was raised by the codec.
.. cfunction:: PyObject* PyString_AsEncodedObject(PyObject *str, const char *encoding, const char *errors)
Encode a string object using the codec registered for *encoding* and return the
result as Python object. *encoding* and *errors* have the same meaning as the
parameters of the same name in the string :meth:`encode` method. The codec to be
used is looked up using the Python codec registry. Return *NULL* if an exception
was raised by the codec.

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.. highlightlang:: c
.. _common-structs:
Common Object Structures
========================
There are a large number of structures which are used in the definition of
object types for Python. This section describes these structures and how they
are used.
All Python objects ultimately share a small number of fields at the beginning of
the object's representation in memory. These are represented by the
:ctype:`PyObject` and :ctype:`PyVarObject` types, which are defined, in turn, by
the expansions of some macros also used, whether directly or indirectly, in the
definition of all other Python objects.
.. ctype:: PyObject
All object types are extensions of this type. This is a type which contains the
information Python needs to treat a pointer to an object as an object. In a
normal "release" build, it contains only the objects reference count and a
pointer to the corresponding type object. It corresponds to the fields defined
by the expansion of the ``PyObject_HEAD`` macro.
.. ctype:: PyVarObject
This is an extension of :ctype:`PyObject` that adds the :attr:`ob_size` field.
This is only used for objects that have some notion of *length*. This type does
not often appear in the Python/C API. It corresponds to the fields defined by
the expansion of the ``PyObject_VAR_HEAD`` macro.
These macros are used in the definition of :ctype:`PyObject` and
:ctype:`PyVarObject`:
.. XXX need to document PEP 3123 changes here
.. cmacro:: PyObject_HEAD
This is a macro which expands to the declarations of the fields of the
:ctype:`PyObject` type; it is used when declaring new types which represent
objects without a varying length. The specific fields it expands to depend on
the definition of :cmacro:`Py_TRACE_REFS`. By default, that macro is not
defined, and :cmacro:`PyObject_HEAD` expands to::
Py_ssize_t ob_refcnt;
PyTypeObject *ob_type;
When :cmacro:`Py_TRACE_REFS` is defined, it expands to::
PyObject *_ob_next, *_ob_prev;
Py_ssize_t ob_refcnt;
PyTypeObject *ob_type;
.. cmacro:: PyObject_VAR_HEAD
This is a macro which expands to the declarations of the fields of the
:ctype:`PyVarObject` type; it is used when declaring new types which represent
objects with a length that varies from instance to instance. This macro always
expands to::
PyObject_HEAD
Py_ssize_t ob_size;
Note that :cmacro:`PyObject_HEAD` is part of the expansion, and that its own
expansion varies depending on the definition of :cmacro:`Py_TRACE_REFS`.
.. cmacro:: PyObject_HEAD_INIT
.. ctype:: PyCFunction
Type of the functions used to implement most Python callables in C. Functions of
this type take two :ctype:`PyObject\*` parameters and return one such value. If
the return value is *NULL*, an exception shall have been set. If not *NULL*,
the return value is interpreted as the return value of the function as exposed
in Python. The function must return a new reference.
.. ctype:: PyCFunctionWithKeywords
Type of the functions used to implement Python callables in C that take
keyword arguments: they take three :ctype:`PyObject\*` parameters and return
one such value. See :ctype:`PyCFunction` above for the meaning of the return
value.
.. ctype:: PyMethodDef
Structure used to describe a method of an extension type. This structure has
four fields:
+------------------+-------------+-------------------------------+
| Field | C Type | Meaning |
+==================+=============+===============================+
| :attr:`ml_name` | char \* | name of the method |
+------------------+-------------+-------------------------------+
| :attr:`ml_meth` | PyCFunction | pointer to the C |
| | | implementation |
+------------------+-------------+-------------------------------+
| :attr:`ml_flags` | int | flag bits indicating how the |
| | | call should be constructed |
+------------------+-------------+-------------------------------+
| :attr:`ml_doc` | char \* | points to the contents of the |
| | | docstring |
+------------------+-------------+-------------------------------+
The :attr:`ml_meth` is a C function pointer. The functions may be of different
types, but they always return :ctype:`PyObject\*`. If the function is not of
the :ctype:`PyCFunction`, the compiler will require a cast in the method table.
Even though :ctype:`PyCFunction` defines the first parameter as
:ctype:`PyObject\*`, it is common that the method implementation uses a the
specific C type of the *self* object.
The :attr:`ml_flags` field is a bitfield which can include the following flags.
The individual flags indicate either a calling convention or a binding
convention. Of the calling convention flags, only :const:`METH_VARARGS` and
:const:`METH_KEYWORDS` can be combined (but note that :const:`METH_KEYWORDS`
alone is equivalent to ``METH_VARARGS | METH_KEYWORDS``). Any of the calling
convention flags can be combined with a binding flag.
.. data:: METH_VARARGS
This is the typical calling convention, where the methods have the type
:ctype:`PyCFunction`. The function expects two :ctype:`PyObject\*` values. The
first one is the *self* object for methods; for module functions, it has the
value given to :cfunc:`Py_InitModule4` (or *NULL* if :cfunc:`Py_InitModule` was
used). The second parameter (often called *args*) is a tuple object
representing all arguments. This parameter is typically processed using
:cfunc:`PyArg_ParseTuple` or :cfunc:`PyArg_UnpackTuple`.
.. data:: METH_KEYWORDS
Methods with these flags must be of type :ctype:`PyCFunctionWithKeywords`. The
function expects three parameters: *self*, *args*, and a dictionary of all the
keyword arguments. The flag is typically combined with :const:`METH_VARARGS`,
and the parameters are typically processed using
:cfunc:`PyArg_ParseTupleAndKeywords`.
.. data:: METH_NOARGS
Methods without parameters don't need to check whether arguments are given if
they are listed with the :const:`METH_NOARGS` flag. They need to be of type
:ctype:`PyCFunction`. When used with object methods, the first parameter is
typically named ``self`` and will hold a reference to the object instance. In
all cases the second parameter will be *NULL*.
.. data:: METH_O
Methods with a single object argument can be listed with the :const:`METH_O`
flag, instead of invoking :cfunc:`PyArg_ParseTuple` with a ``"O"`` argument.
They have the type :ctype:`PyCFunction`, with the *self* parameter, and a
:ctype:`PyObject\*` parameter representing the single argument.
These two constants are not used to indicate the calling convention but the
binding when use with methods of classes. These may not be used for functions
defined for modules. At most one of these flags may be set for any given
method.
.. data:: METH_CLASS
.. index:: builtin: classmethod
The method will be passed the type object as the first parameter rather than an
instance of the type. This is used to create *class methods*, similar to what
is created when using the :func:`classmethod` built-in function.
.. data:: METH_STATIC
.. index:: builtin: staticmethod
The method will be passed *NULL* as the first parameter rather than an instance
of the type. This is used to create *static methods*, similar to what is
created when using the :func:`staticmethod` built-in function.
One other constant controls whether a method is loaded in place of another
definition with the same method name.
.. data:: METH_COEXIST
The method will be loaded in place of existing definitions. Without
*METH_COEXIST*, the default is to skip repeated definitions. Since slot
wrappers are loaded before the method table, the existence of a *sq_contains*
slot, for example, would generate a wrapped method named :meth:`__contains__`
and preclude the loading of a corresponding PyCFunction with the same name.
With the flag defined, the PyCFunction will be loaded in place of the wrapper
object and will co-exist with the slot. This is helpful because calls to
PyCFunctions are optimized more than wrapper object calls.
.. cfunction:: PyObject* Py_FindMethod(PyMethodDef table[], PyObject *ob, char *name)
Return a bound method object for an extension type implemented in C. This can
be useful in the implementation of a :attr:`tp_getattro` or :attr:`tp_getattr`
handler that does not use the :cfunc:`PyObject_GenericGetAttr` function.

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.. highlightlang:: c
.. _os:
Operating System Utilities
==========================
.. cfunction:: int Py_FdIsInteractive(FILE *fp, const char *filename)
Return true (nonzero) if the standard I/O file *fp* with name *filename* is
deemed interactive. This is the case for files for which ``isatty(fileno(fp))``
is true. If the global flag :cdata:`Py_InteractiveFlag` is true, this function
also returns true if the *filename* pointer is *NULL* or if the name is equal to
one of the strings ``'<stdin>'`` or ``'???'``.
.. cfunction:: long PyOS_GetLastModificationTime(char *filename)
Return the time of last modification of the file *filename*. The result is
encoded in the same way as the timestamp returned by the standard C library
function :cfunc:`time`.
.. cfunction:: void PyOS_AfterFork()
Function to update some internal state after a process fork; this should be
called in the new process if the Python interpreter will continue to be used.
If a new executable is loaded into the new process, this function does not need
to be called.
.. cfunction:: int PyOS_CheckStack()
Return true when the interpreter runs out of stack space. This is a reliable
check, but is only available when :const:`USE_STACKCHECK` is defined (currently
on Windows using the Microsoft Visual C++ compiler). :const:`USE_STACKCHECK`
will be defined automatically; you should never change the definition in your
own code.
.. cfunction:: PyOS_sighandler_t PyOS_getsig(int i)
Return the current signal handler for signal *i*. This is a thin wrapper around
either :cfunc:`sigaction` or :cfunc:`signal`. Do not call those functions
directly! :ctype:`PyOS_sighandler_t` is a typedef alias for :ctype:`void
(\*)(int)`.
.. cfunction:: PyOS_sighandler_t PyOS_setsig(int i, PyOS_sighandler_t h)
Set the signal handler for signal *i* to be *h*; return the old signal handler.
This is a thin wrapper around either :cfunc:`sigaction` or :cfunc:`signal`. Do
not call those functions directly! :ctype:`PyOS_sighandler_t` is a typedef
alias for :ctype:`void (\*)(int)`.
.. _systemfunctions:
System Functions
================
These are utility functions that make functionality from the :mod:`sys` module
accessible to C code. They all work with the current interpreter thread's
:mod:`sys` module's dict, which is contained in the internal thread state structure.
.. cfunction:: PyObject *PySys_GetObject(char *name)
Return the object *name* from the :mod:`sys` module or *NULL* if it does
not exist, without setting an exception.
.. cfunction:: FILE *PySys_GetFile(char *name, FILE *def)
Return the :ctype:`FILE*` associated with the object *name* in the
:mod:`sys` module, or *def* if *name* is not in the module or is not associated
with a :ctype:`FILE*`.
.. cfunction:: int PySys_SetObject(char *name, PyObject *v)
Set *name* in the :mod:`sys` module to *v* unless *v* is *NULL*, in which
case *name* is deleted from the sys module. Returns ``0`` on success, ``-1``
on error.
.. cfunction:: void PySys_ResetWarnOptions(void)
Reset :data:`sys.warnoptions` to an empty list.
.. cfunction:: void PySys_AddWarnOption(char *s)
Append *s* to :data:`sys.warnoptions`.
.. cfunction:: void PySys_SetPath(char *path)
Set :data:`sys.path` to a list object of paths found in *path* which should
be a list of paths separated with the platform's search path delimiter
(``:`` on Unix, ``;`` on Windows).
.. cfunction:: void PySys_WriteStdout(const char *format, ...)
Write the output string described by *format* to :data:`sys.stdout`. No
exceptions are raised, even if truncation occurs (see below).
*format* should limit the total size of the formatted output string to
1000 bytes or less -- after 1000 bytes, the output string is truncated.
In particular, this means that no unrestricted "%s" formats should occur;
these should be limited using "%.<N>s" where <N> is a decimal number
calculated so that <N> plus the maximum size of other formatted text does not
exceed 1000 bytes. Also watch out for "%f", which can print hundreds of
digits for very large numbers.
If a problem occurs, or :data:`sys.stdout` is unset, the formatted message
is written to the real (C level) *stdout*.
.. cfunction:: void PySys_WriteStderr(const char *format, ...)
As above, but write to :data:`sys.stderr` or *stderr* instead.
.. _processcontrol:
Process Control
===============
.. cfunction:: void Py_FatalError(const char *message)
.. index:: single: abort()
Print a fatal error message and kill the process. No cleanup is performed.
This function should only be invoked when a condition is detected that would
make it dangerous to continue using the Python interpreter; e.g., when the
object administration appears to be corrupted. On Unix, the standard C library
function :cfunc:`abort` is called which will attempt to produce a :file:`core`
file.
.. cfunction:: void Py_Exit(int status)
.. index::
single: Py_Finalize()
single: exit()
Exit the current process. This calls :cfunc:`Py_Finalize` and then calls the
standard C library function ``exit(status)``.
.. cfunction:: int Py_AtExit(void (*func) ())
.. index::
single: Py_Finalize()
single: cleanup functions
Register a cleanup function to be called by :cfunc:`Py_Finalize`. The cleanup
function will be called with no arguments and should return no value. At most
32 cleanup functions can be registered. When the registration is successful,
:cfunc:`Py_AtExit` returns ``0``; on failure, it returns ``-1``. The cleanup
function registered last is called first. Each cleanup function will be called
at most once. Since Python's internal finalization will have completed before
the cleanup function, no Python APIs should be called by *func*.

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.. highlightlang:: c
.. _tupleobjects:
Tuple Objects
-------------
.. index:: object: tuple
.. ctype:: PyTupleObject
This subtype of :ctype:`PyObject` represents a Python tuple object.
.. cvar:: PyTypeObject PyTuple_Type
.. index:: single: TupleType (in module types)
This instance of :ctype:`PyTypeObject` represents the Python tuple type; it is
the same object as ``tuple`` and ``types.TupleType`` in the Python layer..
.. cfunction:: int PyTuple_Check(PyObject *p)
Return true if *p* is a tuple object or an instance of a subtype of the tuple
type.
.. cfunction:: int PyTuple_CheckExact(PyObject *p)
Return true if *p* is a tuple object, but not an instance of a subtype of the
tuple type.
.. cfunction:: PyObject* PyTuple_New(Py_ssize_t len)
Return a new tuple object of size *len*, or *NULL* on failure.
.. cfunction:: PyObject* PyTuple_Pack(Py_ssize_t n, ...)
Return a new tuple object of size *n*, or *NULL* on failure. The tuple values
are initialized to the subsequent *n* C arguments pointing to Python objects.
``PyTuple_Pack(2, a, b)`` is equivalent to ``Py_BuildValue("(OO)", a, b)``.
.. cfunction:: Py_ssize_t PyTuple_Size(PyObject *p)
Take a pointer to a tuple object, and return the size of that tuple.
.. cfunction:: Py_ssize_t PyTuple_GET_SIZE(PyObject *p)
Return the size of the tuple *p*, which must be non-*NULL* and point to a tuple;
no error checking is performed.
.. cfunction:: PyObject* PyTuple_GetItem(PyObject *p, Py_ssize_t pos)
Return the object at position *pos* in the tuple pointed to by *p*. If *pos* is
out of bounds, return *NULL* and sets an :exc:`IndexError` exception.
.. cfunction:: PyObject* PyTuple_GET_ITEM(PyObject *p, Py_ssize_t pos)
Like :cfunc:`PyTuple_GetItem`, but does no checking of its arguments.
.. cfunction:: PyObject* PyTuple_GetSlice(PyObject *p, Py_ssize_t low, Py_ssize_t high)
Take a slice of the tuple pointed to by *p* from *low* to *high* and return it
as a new tuple.
.. cfunction:: int PyTuple_SetItem(PyObject *p, Py_ssize_t pos, PyObject *o)
Insert a reference to object *o* at position *pos* of the tuple pointed to by
*p*. Return ``0`` on success.
.. note::
This function "steals" a reference to *o*.
.. cfunction:: void PyTuple_SET_ITEM(PyObject *p, Py_ssize_t pos, PyObject *o)
Like :cfunc:`PyTuple_SetItem`, but does no error checking, and should *only* be
used to fill in brand new tuples.
.. note::
This function "steals" a reference to *o*.
.. cfunction:: int _PyTuple_Resize(PyObject **p, Py_ssize_t newsize)
Can be used to resize a tuple. *newsize* will be the new length of the tuple.
Because tuples are *supposed* to be immutable, this should only be used if there
is only one reference to the object. Do *not* use this if the tuple may already
be known to some other part of the code. The tuple will always grow or shrink
at the end. Think of this as destroying the old tuple and creating a new one,
only more efficiently. Returns ``0`` on success. Client code should never
assume that the resulting value of ``*p`` will be the same as before calling
this function. If the object referenced by ``*p`` is replaced, the original
``*p`` is destroyed. On failure, returns ``-1`` and sets ``*p`` to *NULL*, and
raises :exc:`MemoryError` or :exc:`SystemError`.

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.. highlightlang:: c
.. _typeobjects:
Type Objects
------------
.. index:: object: type
.. ctype:: PyTypeObject
The C structure of the objects used to describe built-in types.
.. cvar:: PyObject* PyType_Type
.. index:: single: TypeType (in module types)
This is the type object for type objects; it is the same object as ``type`` and
``types.TypeType`` in the Python layer.
.. cfunction:: int PyType_Check(PyObject *o)
Return true if the object *o* is a type object, including instances of types
derived from the standard type object. Return false in all other cases.
.. cfunction:: int PyType_CheckExact(PyObject *o)
Return true if the object *o* is a type object, but not a subtype of the
standard type object. Return false in all other cases.
.. cfunction:: int PyType_HasFeature(PyObject *o, int feature)
Return true if the type object *o* sets the feature *feature*. Type features
are denoted by single bit flags.
.. cfunction:: int PyType_IS_GC(PyObject *o)
Return true if the type object includes support for the cycle detector; this
tests the type flag :const:`Py_TPFLAGS_HAVE_GC`.
.. cfunction:: int PyType_IsSubtype(PyTypeObject *a, PyTypeObject *b)
Return true if *a* is a subtype of *b*.
.. cfunction:: PyObject* PyType_GenericAlloc(PyTypeObject *type, Py_ssize_t nitems)
XXX: Document.
.. cfunction:: PyObject* PyType_GenericNew(PyTypeObject *type, PyObject *args, PyObject *kwds)
XXX: Document.
.. cfunction:: int PyType_Ready(PyTypeObject *type)
Finalize a type object. This should be called on all type objects to finish
their initialization. This function is responsible for adding inherited slots
from a type's base class. Return ``0`` on success, or return ``-1`` and sets an
exception on error.

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.. highlightlang:: c
.. _unicodeobjects:
Unicode Objects and Codecs
--------------------------
.. sectionauthor:: Marc-Andre Lemburg <mal@lemburg.com>
Unicode Objects
^^^^^^^^^^^^^^^
These are the basic Unicode object types used for the Unicode implementation in
Python:
.. % --- Unicode Type -------------------------------------------------------
.. ctype:: Py_UNICODE
This type represents the storage type which is used by Python internally as
basis for holding Unicode ordinals. Python's default builds use a 16-bit type
for :ctype:`Py_UNICODE` and store Unicode values internally as UCS2. It is also
possible to build a UCS4 version of Python (most recent Linux distributions come
with UCS4 builds of Python). These builds then use a 32-bit type for
:ctype:`Py_UNICODE` and store Unicode data internally as UCS4. On platforms
where :ctype:`wchar_t` is available and compatible with the chosen Python
Unicode build variant, :ctype:`Py_UNICODE` is a typedef alias for
:ctype:`wchar_t` to enhance native platform compatibility. On all other
platforms, :ctype:`Py_UNICODE` is a typedef alias for either :ctype:`unsigned
short` (UCS2) or :ctype:`unsigned long` (UCS4).
Note that UCS2 and UCS4 Python builds are not binary compatible. Please keep
this in mind when writing extensions or interfaces.
.. ctype:: PyUnicodeObject
This subtype of :ctype:`PyObject` represents a Python Unicode object.
.. cvar:: PyTypeObject PyUnicode_Type
This instance of :ctype:`PyTypeObject` represents the Python Unicode type. It
is exposed to Python code as ``str``.
The following APIs are really C macros and can be used to do fast checks and to
access internal read-only data of Unicode objects:
.. cfunction:: int PyUnicode_Check(PyObject *o)
Return true if the object *o* is a Unicode object or an instance of a Unicode
subtype.
.. cfunction:: int PyUnicode_CheckExact(PyObject *o)
Return true if the object *o* is a Unicode object, but not an instance of a
subtype.
.. cfunction:: Py_ssize_t PyUnicode_GET_SIZE(PyObject *o)
Return the size of the object. *o* has to be a :ctype:`PyUnicodeObject` (not
checked).
.. cfunction:: Py_ssize_t PyUnicode_GET_DATA_SIZE(PyObject *o)
Return the size of the object's internal buffer in bytes. *o* has to be a
:ctype:`PyUnicodeObject` (not checked).
.. cfunction:: Py_UNICODE* PyUnicode_AS_UNICODE(PyObject *o)
Return a pointer to the internal :ctype:`Py_UNICODE` buffer of the object. *o*
has to be a :ctype:`PyUnicodeObject` (not checked).
.. cfunction:: const char* PyUnicode_AS_DATA(PyObject *o)
Return a pointer to the internal buffer of the object. *o* has to be a
:ctype:`PyUnicodeObject` (not checked).
Unicode provides many different character properties. The most often needed ones
are available through these macros which are mapped to C functions depending on
the Python configuration.
.. % --- Unicode character properties ---------------------------------------
.. cfunction:: int Py_UNICODE_ISSPACE(Py_UNICODE ch)
Return 1 or 0 depending on whether *ch* is a whitespace character.
.. cfunction:: int Py_UNICODE_ISLOWER(Py_UNICODE ch)
Return 1 or 0 depending on whether *ch* is a lowercase character.
.. cfunction:: int Py_UNICODE_ISUPPER(Py_UNICODE ch)
Return 1 or 0 depending on whether *ch* is an uppercase character.
.. cfunction:: int Py_UNICODE_ISTITLE(Py_UNICODE ch)
Return 1 or 0 depending on whether *ch* is a titlecase character.
.. cfunction:: int Py_UNICODE_ISLINEBREAK(Py_UNICODE ch)
Return 1 or 0 depending on whether *ch* is a linebreak character.
.. cfunction:: int Py_UNICODE_ISDECIMAL(Py_UNICODE ch)
Return 1 or 0 depending on whether *ch* is a decimal character.
.. cfunction:: int Py_UNICODE_ISDIGIT(Py_UNICODE ch)
Return 1 or 0 depending on whether *ch* is a digit character.
.. cfunction:: int Py_UNICODE_ISNUMERIC(Py_UNICODE ch)
Return 1 or 0 depending on whether *ch* is a numeric character.
.. cfunction:: int Py_UNICODE_ISALPHA(Py_UNICODE ch)
Return 1 or 0 depending on whether *ch* is an alphabetic character.
.. cfunction:: int Py_UNICODE_ISALNUM(Py_UNICODE ch)
Return 1 or 0 depending on whether *ch* is an alphanumeric character.
These APIs can be used for fast direct character conversions:
.. cfunction:: Py_UNICODE Py_UNICODE_TOLOWER(Py_UNICODE ch)
Return the character *ch* converted to lower case.
.. cfunction:: Py_UNICODE Py_UNICODE_TOUPPER(Py_UNICODE ch)
Return the character *ch* converted to upper case.
.. cfunction:: Py_UNICODE Py_UNICODE_TOTITLE(Py_UNICODE ch)
Return the character *ch* converted to title case.
.. cfunction:: int Py_UNICODE_TODECIMAL(Py_UNICODE ch)
Return the character *ch* converted to a decimal positive integer. Return
``-1`` if this is not possible. This macro does not raise exceptions.
.. cfunction:: int Py_UNICODE_TODIGIT(Py_UNICODE ch)
Return the character *ch* converted to a single digit integer. Return ``-1`` if
this is not possible. This macro does not raise exceptions.
.. cfunction:: double Py_UNICODE_TONUMERIC(Py_UNICODE ch)
Return the character *ch* converted to a double. Return ``-1.0`` if this is not
possible. This macro does not raise exceptions.
To create Unicode objects and access their basic sequence properties, use these
APIs:
.. % --- Plain Py_UNICODE ---------------------------------------------------
.. cfunction:: PyObject* PyUnicode_FromUnicode(const Py_UNICODE *u, Py_ssize_t size)
Create a Unicode Object from the Py_UNICODE buffer *u* of the given size. *u*
may be *NULL* which causes the contents to be undefined. It is the user's
responsibility to fill in the needed data. The buffer is copied into the new
object. If the buffer is not *NULL*, the return value might be a shared object.
Therefore, modification of the resulting Unicode object is only allowed when *u*
is *NULL*.
.. cfunction:: PyObject* PyUnicode_FromStringAndSize(const char *u, Py_ssize_t size)
Create a Unicode Object from the char buffer *u*. The bytes will be interpreted
as being UTF-8 encoded. *u* may also be *NULL* which
causes the contents to be undefined. It is the user's responsibility to fill in
the needed data. The buffer is copied into the new object. If the buffer is not
*NULL*, the return value might be a shared object. Therefore, modification of
the resulting Unicode object is only allowed when *u* is *NULL*.
.. cfunction:: PyObject *PyUnicode_FromString(const char *u)
Create a Unicode object from an UTF-8 encoded null-terminated char buffer
*u*.
.. cfunction:: PyObject* PyUnicode_FromFormat(const char *format, ...)
Take a C :cfunc:`printf`\ -style *format* string and a variable number of
arguments, calculate the size of the resulting Python unicode string and return
a string with the values formatted into it. The variable arguments must be C
types and must correspond exactly to the format characters in the *format*
string. The following format characters are allowed:
.. % The descriptions for %zd and %zu are wrong, but the truth is complicated
.. % because not all compilers support the %z width modifier -- we fake it
.. % when necessary via interpolating PY_FORMAT_SIZE_T.
+-------------------+---------------------+--------------------------------+
| Format Characters | Type | Comment |
+===================+=====================+================================+
| :attr:`%%` | *n/a* | The literal % character. |
+-------------------+---------------------+--------------------------------+
| :attr:`%c` | int | A single character, |
| | | represented as an C int. |
+-------------------+---------------------+--------------------------------+
| :attr:`%d` | int | Exactly equivalent to |
| | | ``printf("%d")``. |
+-------------------+---------------------+--------------------------------+
| :attr:`%u` | unsigned int | Exactly equivalent to |
| | | ``printf("%u")``. |
+-------------------+---------------------+--------------------------------+
| :attr:`%ld` | long | Exactly equivalent to |
| | | ``printf("%ld")``. |
+-------------------+---------------------+--------------------------------+
| :attr:`%lu` | unsigned long | Exactly equivalent to |
| | | ``printf("%lu")``. |
+-------------------+---------------------+--------------------------------+
| :attr:`%zd` | Py_ssize_t | Exactly equivalent to |
| | | ``printf("%zd")``. |
+-------------------+---------------------+--------------------------------+
| :attr:`%zu` | size_t | Exactly equivalent to |
| | | ``printf("%zu")``. |
+-------------------+---------------------+--------------------------------+
| :attr:`%i` | int | Exactly equivalent to |
| | | ``printf("%i")``. |
+-------------------+---------------------+--------------------------------+
| :attr:`%x` | int | Exactly equivalent to |
| | | ``printf("%x")``. |
+-------------------+---------------------+--------------------------------+
| :attr:`%s` | char\* | A null-terminated C character |
| | | array. |
+-------------------+---------------------+--------------------------------+
| :attr:`%p` | void\* | The hex representation of a C |
| | | pointer. Mostly equivalent to |
| | | ``printf("%p")`` except that |
| | | it is guaranteed to start with |
| | | the literal ``0x`` regardless |
| | | of what the platform's |
| | | ``printf`` yields. |
+-------------------+---------------------+--------------------------------+
| :attr:`%U` | PyObject\* | A unicode object. |
+-------------------+---------------------+--------------------------------+
| :attr:`%V` | PyObject\*, char \* | A unicode object (which may be |
| | | *NULL*) and a null-terminated |
| | | C character array as a second |
| | | parameter (which will be used, |
| | | if the first parameter is |
| | | *NULL*). |
+-------------------+---------------------+--------------------------------+
| :attr:`%S` | PyObject\* | The result of calling |
| | | :func:`PyObject_Unicode`. |
+-------------------+---------------------+--------------------------------+
| :attr:`%R` | PyObject\* | The result of calling |
| | | :func:`PyObject_Repr`. |
+-------------------+---------------------+--------------------------------+
An unrecognized format character causes all the rest of the format string to be
copied as-is to the result string, and any extra arguments discarded.
.. cfunction:: PyObject* PyUnicode_FromFormatV(const char *format, va_list vargs)
Identical to :func:`PyUnicode_FromFormat` except that it takes exactly two
arguments.
.. cfunction:: Py_UNICODE* PyUnicode_AsUnicode(PyObject *unicode)
Return a read-only pointer to the Unicode object's internal :ctype:`Py_UNICODE`
buffer, *NULL* if *unicode* is not a Unicode object.
.. cfunction:: Py_ssize_t PyUnicode_GetSize(PyObject *unicode)
Return the length of the Unicode object.
.. cfunction:: PyObject* PyUnicode_FromEncodedObject(PyObject *obj, const char *encoding, const char *errors)
Coerce an encoded object *obj* to an Unicode object and return a reference with
incremented refcount.
String and other char buffer compatible objects are decoded according to the
given encoding and using the error handling defined by errors. Both can be
*NULL* to have the interface use the default values (see the next section for
details).
All other objects, including Unicode objects, cause a :exc:`TypeError` to be
set.
The API returns *NULL* if there was an error. The caller is responsible for
decref'ing the returned objects.
.. cfunction:: PyObject* PyUnicode_FromObject(PyObject *obj)
Shortcut for ``PyUnicode_FromEncodedObject(obj, NULL, "strict")`` which is used
throughout the interpreter whenever coercion to Unicode is needed.
If the platform supports :ctype:`wchar_t` and provides a header file wchar.h,
Python can interface directly to this type using the following functions.
Support is optimized if Python's own :ctype:`Py_UNICODE` type is identical to
the system's :ctype:`wchar_t`.
.. % --- wchar_t support for platforms which support it ---------------------
.. cfunction:: PyObject* PyUnicode_FromWideChar(const wchar_t *w, Py_ssize_t size)
Create a Unicode object from the :ctype:`wchar_t` buffer *w* of the given size.
Return *NULL* on failure.
.. cfunction:: Py_ssize_t PyUnicode_AsWideChar(PyUnicodeObject *unicode, wchar_t *w, Py_ssize_t size)
Copy the Unicode object contents into the :ctype:`wchar_t` buffer *w*. At most
*size* :ctype:`wchar_t` characters are copied (excluding a possibly trailing
0-termination character). Return the number of :ctype:`wchar_t` characters
copied or -1 in case of an error. Note that the resulting :ctype:`wchar_t`
string may or may not be 0-terminated. It is the responsibility of the caller
to make sure that the :ctype:`wchar_t` string is 0-terminated in case this is
required by the application.
.. _builtincodecs:
Built-in Codecs
^^^^^^^^^^^^^^^
Python provides a set of builtin codecs which are written in C for speed. All of
these codecs are directly usable via the following functions.
Many of the following APIs take two arguments encoding and errors. These
parameters encoding and errors have the same semantics as the ones of the
builtin unicode() Unicode object constructor.
Setting encoding to *NULL* causes the default encoding to be used which is
ASCII. The file system calls should use :cdata:`Py_FileSystemDefaultEncoding`
as the encoding for file names. This variable should be treated as read-only: On
some systems, it will be a pointer to a static string, on others, it will change
at run-time (such as when the application invokes setlocale).
Error handling is set by errors which may also be set to *NULL* meaning to use
the default handling defined for the codec. Default error handling for all
builtin codecs is "strict" (:exc:`ValueError` is raised).
The codecs all use a similar interface. Only deviation from the following
generic ones are documented for simplicity.
These are the generic codec APIs:
.. % --- Generic Codecs -----------------------------------------------------
.. cfunction:: PyObject* PyUnicode_Decode(const char *s, Py_ssize_t size, const char *encoding, const char *errors)
Create a Unicode object by decoding *size* bytes of the encoded string *s*.
*encoding* and *errors* have the same meaning as the parameters of the same name
in the :func:`unicode` builtin function. The codec to be used is looked up
using the Python codec registry. Return *NULL* if an exception was raised by
the codec.
.. cfunction:: PyObject* PyUnicode_Encode(const Py_UNICODE *s, Py_ssize_t size, const char *encoding, const char *errors)
Encode the :ctype:`Py_UNICODE` buffer of the given size and return a Python
string object. *encoding* and *errors* have the same meaning as the parameters
of the same name in the Unicode :meth:`encode` method. The codec to be used is
looked up using the Python codec registry. Return *NULL* if an exception was
raised by the codec.
.. cfunction:: PyObject* PyUnicode_AsEncodedString(PyObject *unicode, const char *encoding, const char *errors)
Encode a Unicode object and return the result as Python string object.
*encoding* and *errors* have the same meaning as the parameters of the same name
in the Unicode :meth:`encode` method. The codec to be used is looked up using
the Python codec registry. Return *NULL* if an exception was raised by the
codec.
These are the UTF-8 codec APIs:
.. % --- UTF-8 Codecs -------------------------------------------------------
.. cfunction:: PyObject* PyUnicode_DecodeUTF8(const char *s, Py_ssize_t size, const char *errors)
Create a Unicode object by decoding *size* bytes of the UTF-8 encoded string
*s*. Return *NULL* if an exception was raised by the codec.
.. cfunction:: PyObject* PyUnicode_DecodeUTF8Stateful(const char *s, Py_ssize_t size, const char *errors, Py_ssize_t *consumed)
If *consumed* is *NULL*, behave like :cfunc:`PyUnicode_DecodeUTF8`. If
*consumed* is not *NULL*, trailing incomplete UTF-8 byte sequences will not be
treated as an error. Those bytes will not be decoded and the number of bytes
that have been decoded will be stored in *consumed*.
.. cfunction:: PyObject* PyUnicode_EncodeUTF8(const Py_UNICODE *s, Py_ssize_t size, const char *errors)
Encode the :ctype:`Py_UNICODE` buffer of the given size using UTF-8 and return a
Python string object. Return *NULL* if an exception was raised by the codec.
.. cfunction:: PyObject* PyUnicode_AsUTF8String(PyObject *unicode)
Encode a Unicode object using UTF-8 and return the result as Python string
object. Error handling is "strict". Return *NULL* if an exception was raised
by the codec.
These are the UTF-32 codec APIs:
.. % --- UTF-32 Codecs ------------------------------------------------------ */
.. cfunction:: PyObject* PyUnicode_DecodeUTF32(const char *s, Py_ssize_t size, const char *errors, int *byteorder)
Decode *length* bytes from a UTF-32 encoded buffer string and return the
corresponding Unicode object. *errors* (if non-*NULL*) defines the error
handling. It defaults to "strict".
If *byteorder* is non-*NULL*, the decoder starts decoding using the given byte
order::
*byteorder == -1: little endian
*byteorder == 0: native order
*byteorder == 1: big endian
and then switches if the first four bytes of the input data are a byte order mark
(BOM) and the specified byte order is native order. This BOM is not copied into
the resulting Unicode string. After completion, *\*byteorder* is set to the
current byte order at the end of input data.
In a narrow build codepoints outside the BMP will be decoded as surrogate pairs.
If *byteorder* is *NULL*, the codec starts in native order mode.
Return *NULL* if an exception was raised by the codec.
.. cfunction:: PyObject* PyUnicode_DecodeUTF32Stateful(const char *s, Py_ssize_t size, const char *errors, int *byteorder, Py_ssize_t *consumed)
If *consumed* is *NULL*, behave like :cfunc:`PyUnicode_DecodeUTF32`. If
*consumed* is not *NULL*, :cfunc:`PyUnicode_DecodeUTF32Stateful` will not treat
trailing incomplete UTF-32 byte sequences (such as a number of bytes not divisible
by four) as an error. Those bytes will not be decoded and the number of bytes
that have been decoded will be stored in *consumed*.
.. cfunction:: PyObject* PyUnicode_EncodeUTF32(const Py_UNICODE *s, Py_ssize_t size, const char *errors, int byteorder)
Return a Python bytes object holding the UTF-32 encoded value of the Unicode
data in *s*. If *byteorder* is not ``0``, output is written according to the
following byte order::
byteorder == -1: little endian
byteorder == 0: native byte order (writes a BOM mark)
byteorder == 1: big endian
If byteorder is ``0``, the output string will always start with the Unicode BOM
mark (U+FEFF). In the other two modes, no BOM mark is prepended.
If *Py_UNICODE_WIDE* is not defined, surrogate pairs will be output
as a single codepoint.
Return *NULL* if an exception was raised by the codec.
.. cfunction:: PyObject* PyUnicode_AsUTF32String(PyObject *unicode)
Return a Python string using the UTF-32 encoding in native byte order. The
string always starts with a BOM mark. Error handling is "strict". Return
*NULL* if an exception was raised by the codec.
These are the UTF-16 codec APIs:
.. % --- UTF-16 Codecs ------------------------------------------------------ */
.. cfunction:: PyObject* PyUnicode_DecodeUTF16(const char *s, Py_ssize_t size, const char *errors, int *byteorder)
Decode *length* bytes from a UTF-16 encoded buffer string and return the
corresponding Unicode object. *errors* (if non-*NULL*) defines the error
handling. It defaults to "strict".
If *byteorder* is non-*NULL*, the decoder starts decoding using the given byte
order::
*byteorder == -1: little endian
*byteorder == 0: native order
*byteorder == 1: big endian
and then switches if the first two bytes of the input data are a byte order mark
(BOM) and the specified byte order is native order. This BOM is not copied into
the resulting Unicode string. After completion, *\*byteorder* is set to the
current byte order at the end of input data.
If *byteorder* is *NULL*, the codec starts in native order mode.
Return *NULL* if an exception was raised by the codec.
.. cfunction:: PyObject* PyUnicode_DecodeUTF16Stateful(const char *s, Py_ssize_t size, const char *errors, int *byteorder, Py_ssize_t *consumed)
If *consumed* is *NULL*, behave like :cfunc:`PyUnicode_DecodeUTF16`. If
*consumed* is not *NULL*, :cfunc:`PyUnicode_DecodeUTF16Stateful` will not treat
trailing incomplete UTF-16 byte sequences (such as an odd number of bytes or a
split surrogate pair) as an error. Those bytes will not be decoded and the
number of bytes that have been decoded will be stored in *consumed*.
.. cfunction:: PyObject* PyUnicode_EncodeUTF16(const Py_UNICODE *s, Py_ssize_t size, const char *errors, int byteorder)
Return a Python string object holding the UTF-16 encoded value of the Unicode
data in *s*. If *byteorder* is not ``0``, output is written according to the
following byte order::
byteorder == -1: little endian
byteorder == 0: native byte order (writes a BOM mark)
byteorder == 1: big endian
If byteorder is ``0``, the output string will always start with the Unicode BOM
mark (U+FEFF). In the other two modes, no BOM mark is prepended.
If *Py_UNICODE_WIDE* is defined, a single :ctype:`Py_UNICODE` value may get
represented as a surrogate pair. If it is not defined, each :ctype:`Py_UNICODE`
values is interpreted as an UCS-2 character.
Return *NULL* if an exception was raised by the codec.
.. cfunction:: PyObject* PyUnicode_AsUTF16String(PyObject *unicode)
Return a Python string using the UTF-16 encoding in native byte order. The
string always starts with a BOM mark. Error handling is "strict". Return
*NULL* if an exception was raised by the codec.
These are the "Unicode Escape" codec APIs:
.. % --- Unicode-Escape Codecs ----------------------------------------------
.. cfunction:: PyObject* PyUnicode_DecodeUnicodeEscape(const char *s, Py_ssize_t size, const char *errors)
Create a Unicode object by decoding *size* bytes of the Unicode-Escape encoded
string *s*. Return *NULL* if an exception was raised by the codec.
.. cfunction:: PyObject* PyUnicode_EncodeUnicodeEscape(const Py_UNICODE *s, Py_ssize_t size)
Encode the :ctype:`Py_UNICODE` buffer of the given size using Unicode-Escape and
return a Python string object. Return *NULL* if an exception was raised by the
codec.
.. cfunction:: PyObject* PyUnicode_AsUnicodeEscapeString(PyObject *unicode)
Encode a Unicode object using Unicode-Escape and return the result as Python
string object. Error handling is "strict". Return *NULL* if an exception was
raised by the codec.
These are the "Raw Unicode Escape" codec APIs:
.. % --- Raw-Unicode-Escape Codecs ------------------------------------------
.. cfunction:: PyObject* PyUnicode_DecodeRawUnicodeEscape(const char *s, Py_ssize_t size, const char *errors)
Create a Unicode object by decoding *size* bytes of the Raw-Unicode-Escape
encoded string *s*. Return *NULL* if an exception was raised by the codec.
.. cfunction:: PyObject* PyUnicode_EncodeRawUnicodeEscape(const Py_UNICODE *s, Py_ssize_t size, const char *errors)
Encode the :ctype:`Py_UNICODE` buffer of the given size using Raw-Unicode-Escape
and return a Python string object. Return *NULL* if an exception was raised by
the codec.
.. cfunction:: PyObject* PyUnicode_AsRawUnicodeEscapeString(PyObject *unicode)
Encode a Unicode object using Raw-Unicode-Escape and return the result as
Python string object. Error handling is "strict". Return *NULL* if an exception
was raised by the codec.
These are the Latin-1 codec APIs: Latin-1 corresponds to the first 256 Unicode
ordinals and only these are accepted by the codecs during encoding.
.. % --- Latin-1 Codecs -----------------------------------------------------
.. cfunction:: PyObject* PyUnicode_DecodeLatin1(const char *s, Py_ssize_t size, const char *errors)
Create a Unicode object by decoding *size* bytes of the Latin-1 encoded string
*s*. Return *NULL* if an exception was raised by the codec.
.. cfunction:: PyObject* PyUnicode_EncodeLatin1(const Py_UNICODE *s, Py_ssize_t size, const char *errors)
Encode the :ctype:`Py_UNICODE` buffer of the given size using Latin-1 and return
a Python string object. Return *NULL* if an exception was raised by the codec.
.. cfunction:: PyObject* PyUnicode_AsLatin1String(PyObject *unicode)
Encode a Unicode object using Latin-1 and return the result as Python string
object. Error handling is "strict". Return *NULL* if an exception was raised
by the codec.
These are the ASCII codec APIs. Only 7-bit ASCII data is accepted. All other
codes generate errors.
.. % --- ASCII Codecs -------------------------------------------------------
.. cfunction:: PyObject* PyUnicode_DecodeASCII(const char *s, Py_ssize_t size, const char *errors)
Create a Unicode object by decoding *size* bytes of the ASCII encoded string
*s*. Return *NULL* if an exception was raised by the codec.
.. cfunction:: PyObject* PyUnicode_EncodeASCII(const Py_UNICODE *s, Py_ssize_t size, const char *errors)
Encode the :ctype:`Py_UNICODE` buffer of the given size using ASCII and return a
Python string object. Return *NULL* if an exception was raised by the codec.
.. cfunction:: PyObject* PyUnicode_AsASCIIString(PyObject *unicode)
Encode a Unicode object using ASCII and return the result as Python string
object. Error handling is "strict". Return *NULL* if an exception was raised
by the codec.
These are the mapping codec APIs:
.. % --- Character Map Codecs -----------------------------------------------
This codec is special in that it can be used to implement many different codecs
(and this is in fact what was done to obtain most of the standard codecs
included in the :mod:`encodings` package). The codec uses mapping to encode and
decode characters.
Decoding mappings must map single string characters to single Unicode
characters, integers (which are then interpreted as Unicode ordinals) or None
(meaning "undefined mapping" and causing an error).
Encoding mappings must map single Unicode characters to single string
characters, integers (which are then interpreted as Latin-1 ordinals) or None
(meaning "undefined mapping" and causing an error).
The mapping objects provided must only support the __getitem__ mapping
interface.
If a character lookup fails with a LookupError, the character is copied as-is
meaning that its ordinal value will be interpreted as Unicode or Latin-1 ordinal
resp. Because of this, mappings only need to contain those mappings which map
characters to different code points.
.. cfunction:: PyObject* PyUnicode_DecodeCharmap(const char *s, Py_ssize_t size, PyObject *mapping, const char *errors)
Create a Unicode object by decoding *size* bytes of the encoded string *s* using
the given *mapping* object. Return *NULL* if an exception was raised by the
codec. If *mapping* is *NULL* latin-1 decoding will be done. Else it can be a
dictionary mapping byte or a unicode string, which is treated as a lookup table.
Byte values greater that the length of the string and U+FFFE "characters" are
treated as "undefined mapping".
.. cfunction:: PyObject* PyUnicode_EncodeCharmap(const Py_UNICODE *s, Py_ssize_t size, PyObject *mapping, const char *errors)
Encode the :ctype:`Py_UNICODE` buffer of the given size using the given
*mapping* object and return a Python string object. Return *NULL* if an
exception was raised by the codec.
.. cfunction:: PyObject* PyUnicode_AsCharmapString(PyObject *unicode, PyObject *mapping)
Encode a Unicode object using the given *mapping* object and return the result
as Python string object. Error handling is "strict". Return *NULL* if an
exception was raised by the codec.
The following codec API is special in that maps Unicode to Unicode.
.. cfunction:: PyObject* PyUnicode_TranslateCharmap(const Py_UNICODE *s, Py_ssize_t size, PyObject *table, const char *errors)
Translate a :ctype:`Py_UNICODE` buffer of the given length by applying a
character mapping *table* to it and return the resulting Unicode object. Return
*NULL* when an exception was raised by the codec.
The *mapping* table must map Unicode ordinal integers to Unicode ordinal
integers or None (causing deletion of the character).
Mapping tables need only provide the :meth:`__getitem__` interface; dictionaries
and sequences work well. Unmapped character ordinals (ones which cause a
:exc:`LookupError`) are left untouched and are copied as-is.
These are the MBCS codec APIs. They are currently only available on Windows and
use the Win32 MBCS converters to implement the conversions. Note that MBCS (or
DBCS) is a class of encodings, not just one. The target encoding is defined by
the user settings on the machine running the codec.
.. % --- MBCS codecs for Windows --------------------------------------------
.. cfunction:: PyObject* PyUnicode_DecodeMBCS(const char *s, Py_ssize_t size, const char *errors)
Create a Unicode object by decoding *size* bytes of the MBCS encoded string *s*.
Return *NULL* if an exception was raised by the codec.
.. cfunction:: PyObject* PyUnicode_DecodeMBCSStateful(const char *s, int size, const char *errors, int *consumed)
If *consumed* is *NULL*, behave like :cfunc:`PyUnicode_DecodeMBCS`. If
*consumed* is not *NULL*, :cfunc:`PyUnicode_DecodeMBCSStateful` will not decode
trailing lead byte and the number of bytes that have been decoded will be stored
in *consumed*.
.. cfunction:: PyObject* PyUnicode_EncodeMBCS(const Py_UNICODE *s, Py_ssize_t size, const char *errors)
Encode the :ctype:`Py_UNICODE` buffer of the given size using MBCS and return a
Python string object. Return *NULL* if an exception was raised by the codec.
.. cfunction:: PyObject* PyUnicode_AsMBCSString(PyObject *unicode)
Encode a Unicode object using MBCS and return the result as Python string
object. Error handling is "strict". Return *NULL* if an exception was raised
by the codec.
.. % --- Methods & Slots ----------------------------------------------------
.. _unicodemethodsandslots:
Methods and Slot Functions
^^^^^^^^^^^^^^^^^^^^^^^^^^
The following APIs are capable of handling Unicode objects and strings on input
(we refer to them as strings in the descriptions) and return Unicode objects or
integers as appropriate.
They all return *NULL* or ``-1`` if an exception occurs.
.. cfunction:: PyObject* PyUnicode_Concat(PyObject *left, PyObject *right)
Concat two strings giving a new Unicode string.
.. cfunction:: PyObject* PyUnicode_Split(PyObject *s, PyObject *sep, Py_ssize_t maxsplit)
Split a string giving a list of Unicode strings. If sep is *NULL*, splitting
will be done at all whitespace substrings. Otherwise, splits occur at the given
separator. At most *maxsplit* splits will be done. If negative, no limit is
set. Separators are not included in the resulting list.
.. cfunction:: PyObject* PyUnicode_Splitlines(PyObject *s, int keepend)
Split a Unicode string at line breaks, returning a list of Unicode strings.
CRLF is considered to be one line break. If *keepend* is 0, the Line break
characters are not included in the resulting strings.
.. cfunction:: PyObject* PyUnicode_Translate(PyObject *str, PyObject *table, const char *errors)
Translate a string by applying a character mapping table to it and return the
resulting Unicode object.
The mapping table must map Unicode ordinal integers to Unicode ordinal integers
or None (causing deletion of the character).
Mapping tables need only provide the :meth:`__getitem__` interface; dictionaries
and sequences work well. Unmapped character ordinals (ones which cause a
:exc:`LookupError`) are left untouched and are copied as-is.
*errors* has the usual meaning for codecs. It may be *NULL* which indicates to
use the default error handling.
.. cfunction:: PyObject* PyUnicode_Join(PyObject *separator, PyObject *seq)
Join a sequence of strings using the given separator and return the resulting
Unicode string.
.. cfunction:: int PyUnicode_Tailmatch(PyObject *str, PyObject *substr, Py_ssize_t start, Py_ssize_t end, int direction)
Return 1 if *substr* matches *str*[*start*:*end*] at the given tail end
(*direction* == -1 means to do a prefix match, *direction* == 1 a suffix match),
0 otherwise. Return ``-1`` if an error occurred.
.. cfunction:: Py_ssize_t PyUnicode_Find(PyObject *str, PyObject *substr, Py_ssize_t start, Py_ssize_t end, int direction)
Return the first position of *substr* in *str*[*start*:*end*] using the given
*direction* (*direction* == 1 means to do a forward search, *direction* == -1 a
backward search). The return value is the index of the first match; a value of
``-1`` indicates that no match was found, and ``-2`` indicates that an error
occurred and an exception has been set.
.. cfunction:: Py_ssize_t PyUnicode_Count(PyObject *str, PyObject *substr, Py_ssize_t start, Py_ssize_t end)
Return the number of non-overlapping occurrences of *substr* in
``str[start:end]``. Return ``-1`` if an error occurred.
.. cfunction:: PyObject* PyUnicode_Replace(PyObject *str, PyObject *substr, PyObject *replstr, Py_ssize_t maxcount)
Replace at most *maxcount* occurrences of *substr* in *str* with *replstr* and
return the resulting Unicode object. *maxcount* == -1 means replace all
occurrences.
.. cfunction:: int PyUnicode_Compare(PyObject *left, PyObject *right)
Compare two strings and return -1, 0, 1 for less than, equal, and greater than,
respectively.
.. cfunction:: int PyUnicode_RichCompare(PyObject *left, PyObject *right, int op)
Rich compare two unicode strings and return one of the following:
* ``NULL`` in case an exception was raised
* :const:`Py_True` or :const:`Py_False` for successful comparisons
* :const:`Py_NotImplemented` in case the type combination is unknown
Note that :const:`Py_EQ` and :const:`Py_NE` comparisons can cause a
:exc:`UnicodeWarning` in case the conversion of the arguments to Unicode fails
with a :exc:`UnicodeDecodeError`.
Possible values for *op* are :const:`Py_GT`, :const:`Py_GE`, :const:`Py_EQ`,
:const:`Py_NE`, :const:`Py_LT`, and :const:`Py_LE`.
.. cfunction:: PyObject* PyUnicode_Format(PyObject *format, PyObject *args)
Return a new string object from *format* and *args*; this is analogous to
``format % args``. The *args* argument must be a tuple.
.. cfunction:: int PyUnicode_Contains(PyObject *container, PyObject *element)
Check whether *element* is contained in *container* and return true or false
accordingly.
*element* has to coerce to a one element Unicode string. ``-1`` is returned if
there was an error.
.. cfunction:: void PyUnicode_InternInPlace(PyObject **string)
Intern the argument *\*string* in place. The argument must be the address of a
pointer variable pointing to a Python unicode string object. If there is an
existing interned string that is the same as *\*string*, it sets *\*string* to
it (decrementing the reference count of the old string object and incrementing
the reference count of the interned string object), otherwise it leaves
*\*string* alone and interns it (incrementing its reference count).
(Clarification: even though there is a lot of talk about reference counts, think
of this function as reference-count-neutral; you own the object after the call
if and only if you owned it before the call.)
.. cfunction:: PyObject* PyUnicode_InternFromString(const char *v)
A combination of :cfunc:`PyUnicode_FromString` and
:cfunc:`PyUnicode_InternInPlace`, returning either a new unicode string object
that has been interned, or a new ("owned") reference to an earlier interned
string object with the same value.

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.. highlightlang:: c
.. _weakrefobjects:
Weak Reference Objects
----------------------
Python supports *weak references* as first-class objects. There are two
specific object types which directly implement weak references. The first is a
simple reference object, and the second acts as a proxy for the original object
as much as it can.
.. cfunction:: int PyWeakref_Check(ob)
Return true if *ob* is either a reference or proxy object.
.. cfunction:: int PyWeakref_CheckRef(ob)
Return true if *ob* is a reference object.
.. cfunction:: int PyWeakref_CheckProxy(ob)
Return true if *ob* is a proxy object.
.. cfunction:: PyObject* PyWeakref_NewRef(PyObject *ob, PyObject *callback)
Return a weak reference object for the object *ob*. This will always return
a new reference, but is not guaranteed to create a new object; an existing
reference object may be returned. The second parameter, *callback*, can be a
callable object that receives notification when *ob* is garbage collected; it
should accept a single parameter, which will be the weak reference object
itself. *callback* may also be ``None`` or *NULL*. If *ob* is not a
weakly-referencable object, or if *callback* is not callable, ``None``, or
*NULL*, this will return *NULL* and raise :exc:`TypeError`.
.. cfunction:: PyObject* PyWeakref_NewProxy(PyObject *ob, PyObject *callback)
Return a weak reference proxy object for the object *ob*. This will always
return a new reference, but is not guaranteed to create a new object; an
existing proxy object may be returned. The second parameter, *callback*, can
be a callable object that receives notification when *ob* is garbage
collected; it should accept a single parameter, which will be the weak
reference object itself. *callback* may also be ``None`` or *NULL*. If *ob*
is not a weakly-referencable object, or if *callback* is not callable,
``None``, or *NULL*, this will return *NULL* and raise :exc:`TypeError`.
.. cfunction:: PyObject* PyWeakref_GetObject(PyObject *ref)
Return the referenced object from a weak reference, *ref*. If the referent is
no longer live, returns ``None``.
.. cfunction:: PyObject* PyWeakref_GET_OBJECT(PyObject *ref)
Similar to :cfunc:`PyWeakref_GetObject`, but implemented as a macro that does no
error checking.