mirror of
https://github.com/python/cpython.git
synced 2024-12-14 12:26:47 +08:00
41ca164551
* Add PyDict_GetItemRef() and PyDict_GetItemStringRef() functions. Add these functions to the stable ABI version 3.13. * Add unit tests on the PyDict C API in test_capi.
353 lines
13 KiB
ReStructuredText
353 lines
13 KiB
ReStructuredText
.. highlight:: c
|
|
|
|
.. _dictobjects:
|
|
|
|
Dictionary Objects
|
|
------------------
|
|
|
|
.. index:: pair: object; dictionary
|
|
|
|
|
|
.. c:type:: PyDictObject
|
|
|
|
This subtype of :c:type:`PyObject` represents a Python dictionary object.
|
|
|
|
|
|
.. c:var:: PyTypeObject PyDict_Type
|
|
|
|
This instance of :c:type:`PyTypeObject` represents the Python dictionary
|
|
type. This is the same object as :class:`dict` in the Python layer.
|
|
|
|
|
|
.. c:function:: int PyDict_Check(PyObject *p)
|
|
|
|
Return true if *p* is a dict object or an instance of a subtype of the dict
|
|
type. This function always succeeds.
|
|
|
|
|
|
.. c:function:: int PyDict_CheckExact(PyObject *p)
|
|
|
|
Return true if *p* is a dict object, but not an instance of a subtype of
|
|
the dict type. This function always succeeds.
|
|
|
|
|
|
.. c:function:: PyObject* PyDict_New()
|
|
|
|
Return a new empty dictionary, or ``NULL`` on failure.
|
|
|
|
|
|
.. c:function:: PyObject* PyDictProxy_New(PyObject *mapping)
|
|
|
|
Return a :class:`types.MappingProxyType` object for a mapping which
|
|
enforces read-only behavior. This is normally used to create a view to
|
|
prevent modification of the dictionary for non-dynamic class types.
|
|
|
|
|
|
.. c:function:: void PyDict_Clear(PyObject *p)
|
|
|
|
Empty an existing dictionary of all key-value pairs.
|
|
|
|
|
|
.. c:function:: 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``.
|
|
|
|
|
|
.. c:function:: PyObject* PyDict_Copy(PyObject *p)
|
|
|
|
Return a new dictionary that contains the same key-value pairs as *p*.
|
|
|
|
|
|
.. c:function:: int PyDict_SetItem(PyObject *p, PyObject *key, PyObject *val)
|
|
|
|
Insert *val* 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. This function *does not* steal a
|
|
reference to *val*.
|
|
|
|
|
|
.. c:function:: int PyDict_SetItemString(PyObject *p, const char *key, PyObject *val)
|
|
|
|
.. index:: single: PyUnicode_FromString()
|
|
|
|
Insert *val* into the dictionary *p* using *key* as a key. *key* should
|
|
be a :c:expr:`const char*`. The key object is created using
|
|
``PyUnicode_FromString(key)``. Return ``0`` on success or ``-1`` on
|
|
failure. This function *does not* steal a reference to *val*.
|
|
|
|
|
|
.. c:function:: int PyDict_DelItem(PyObject *p, PyObject *key)
|
|
|
|
Remove the entry in dictionary *p* with key *key*. *key* must be :term:`hashable`;
|
|
if it isn't, :exc:`TypeError` is raised.
|
|
If *key* is not in the dictionary, :exc:`KeyError` is raised.
|
|
Return ``0`` on success or ``-1`` on failure.
|
|
|
|
|
|
.. c:function:: int PyDict_DelItemString(PyObject *p, const char *key)
|
|
|
|
Remove the entry in dictionary *p* which has a key specified by the string *key*.
|
|
If *key* is not in the dictionary, :exc:`KeyError` is raised.
|
|
Return ``0`` on success or ``-1`` on failure.
|
|
|
|
|
|
.. c:function:: int PyDict_GetItemRef(PyObject *p, PyObject *key, PyObject **result)
|
|
|
|
Return a new :term:`strong reference` to the object from dictionary *p*
|
|
which has a key *key*:
|
|
|
|
* If the key is present, set *\*result* to a new :term:`strong reference`
|
|
to the value and return ``1``.
|
|
* If the key is missing, set *\*result* to ``NULL`` and return ``0``.
|
|
* On error, raise an exception and return ``-1``.
|
|
|
|
.. versionadded:: 3.13
|
|
|
|
See also the :c:func:`PyObject_GetItem` function.
|
|
|
|
|
|
.. c:function:: PyObject* PyDict_GetItem(PyObject *p, PyObject *key)
|
|
|
|
Return a :term:`borrowed reference` to the object from dictionary *p* which
|
|
has a key *key*. Return ``NULL`` if the key *key* is missing *without*
|
|
setting an exception.
|
|
|
|
.. note::
|
|
|
|
Exceptions that occur while this calls :meth:`~object.__hash__` and
|
|
:meth:`~object.__eq__` methods are silently ignored.
|
|
Prefer the :c:func:`PyDict_GetItemWithError` function instead.
|
|
|
|
.. versionchanged:: 3.10
|
|
Calling this API without :term:`GIL` held had been allowed for historical
|
|
reason. It is no longer allowed.
|
|
|
|
|
|
.. c:function:: PyObject* PyDict_GetItemWithError(PyObject *p, PyObject *key)
|
|
|
|
Variant of :c:func:`PyDict_GetItem` that does not suppress
|
|
exceptions. Return ``NULL`` **with** an exception set if an exception
|
|
occurred. Return ``NULL`` **without** an exception set if the key
|
|
wasn't present.
|
|
|
|
|
|
.. c:function:: PyObject* PyDict_GetItemString(PyObject *p, const char *key)
|
|
|
|
This is the same as :c:func:`PyDict_GetItem`, but *key* is specified as a
|
|
:c:expr:`const char*`, rather than a :c:expr:`PyObject*`.
|
|
|
|
.. note::
|
|
|
|
Exceptions that occur while this calls :meth:`~object.__hash__` and
|
|
:meth:`~object.__eq__` methods or while creating the temporary :class:`str`
|
|
object are silently ignored.
|
|
Prefer using the :c:func:`PyDict_GetItemWithError` function with your own
|
|
:c:func:`PyUnicode_FromString` *key* instead.
|
|
|
|
|
|
.. c:function:: int PyDict_GetItemStringRef(PyObject *p, const char *key, PyObject **result)
|
|
|
|
Similar than :c:func:`PyDict_GetItemRef`, but *key* is specified as a
|
|
:c:expr:`const char*`, rather than a :c:expr:`PyObject*`.
|
|
|
|
.. versionadded:: 3.13
|
|
|
|
|
|
.. c:function:: PyObject* PyDict_SetDefault(PyObject *p, PyObject *key, PyObject *defaultobj)
|
|
|
|
This is the same as the Python-level :meth:`dict.setdefault`. If present, it
|
|
returns the value corresponding to *key* from the dictionary *p*. If the key
|
|
is not in the dict, it is inserted with value *defaultobj* and *defaultobj*
|
|
is returned. This function evaluates the hash function of *key* only once,
|
|
instead of evaluating it independently for the lookup and the insertion.
|
|
|
|
.. versionadded:: 3.4
|
|
|
|
.. c:function:: PyObject* PyDict_Items(PyObject *p)
|
|
|
|
Return a :c:type:`PyListObject` containing all the items from the dictionary.
|
|
|
|
|
|
.. c:function:: PyObject* PyDict_Keys(PyObject *p)
|
|
|
|
Return a :c:type:`PyListObject` containing all the keys from the dictionary.
|
|
|
|
|
|
.. c:function:: PyObject* PyDict_Values(PyObject *p)
|
|
|
|
Return a :c:type:`PyListObject` containing all the values from the dictionary
|
|
*p*.
|
|
|
|
|
|
.. c:function:: Py_ssize_t PyDict_Size(PyObject *p)
|
|
|
|
.. index:: pair: built-in function; len
|
|
|
|
Return the number of items in the dictionary. This is equivalent to
|
|
``len(p)`` on a dictionary.
|
|
|
|
|
|
.. c:function:: int PyDict_Next(PyObject *p, Py_ssize_t *ppos, PyObject **pkey, PyObject **pvalue)
|
|
|
|
Iterate over all key-value pairs in the dictionary *p*. The
|
|
:c:type:`Py_ssize_t` 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 :c:expr:`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 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);
|
|
}
|
|
|
|
|
|
.. c:function:: 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 :c:func:`PyMapping_Keys`
|
|
and :c: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.
|
|
|
|
|
|
.. c:function:: int PyDict_Update(PyObject *a, PyObject *b)
|
|
|
|
This is the same as ``PyDict_Merge(a, b, 1)`` in C, and is similar to
|
|
``a.update(b)`` in Python except that :c:func:`PyDict_Update` doesn't fall
|
|
back to the iterating over a sequence of key value pairs if the second
|
|
argument has no "keys" attribute. Return ``0`` on success or ``-1`` if an
|
|
exception was raised.
|
|
|
|
|
|
.. c:function:: 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
|
|
|
|
.. c:function:: int PyDict_AddWatcher(PyDict_WatchCallback callback)
|
|
|
|
Register *callback* as a dictionary watcher. Return a non-negative integer
|
|
id which must be passed to future calls to :c:func:`PyDict_Watch`. In case
|
|
of error (e.g. no more watcher IDs available), return ``-1`` and set an
|
|
exception.
|
|
|
|
.. versionadded:: 3.12
|
|
|
|
.. c:function:: int PyDict_ClearWatcher(int watcher_id)
|
|
|
|
Clear watcher identified by *watcher_id* previously returned from
|
|
:c:func:`PyDict_AddWatcher`. Return ``0`` on success, ``-1`` on error (e.g.
|
|
if the given *watcher_id* was never registered.)
|
|
|
|
.. versionadded:: 3.12
|
|
|
|
.. c:function:: int PyDict_Watch(int watcher_id, PyObject *dict)
|
|
|
|
Mark dictionary *dict* as watched. The callback granted *watcher_id* by
|
|
:c:func:`PyDict_AddWatcher` will be called when *dict* is modified or
|
|
deallocated. Return ``0`` on success or ``-1`` on error.
|
|
|
|
.. versionadded:: 3.12
|
|
|
|
.. c:function:: int PyDict_Unwatch(int watcher_id, PyObject *dict)
|
|
|
|
Mark dictionary *dict* as no longer watched. The callback granted
|
|
*watcher_id* by :c:func:`PyDict_AddWatcher` will no longer be called when
|
|
*dict* is modified or deallocated. The dict must previously have been
|
|
watched by this watcher. Return ``0`` on success or ``-1`` on error.
|
|
|
|
.. versionadded:: 3.12
|
|
|
|
.. c:type:: PyDict_WatchEvent
|
|
|
|
Enumeration of possible dictionary watcher events: ``PyDict_EVENT_ADDED``,
|
|
``PyDict_EVENT_MODIFIED``, ``PyDict_EVENT_DELETED``, ``PyDict_EVENT_CLONED``,
|
|
``PyDict_EVENT_CLEARED``, or ``PyDict_EVENT_DEALLOCATED``.
|
|
|
|
.. versionadded:: 3.12
|
|
|
|
.. c:type:: int (*PyDict_WatchCallback)(PyDict_WatchEvent event, PyObject *dict, PyObject *key, PyObject *new_value)
|
|
|
|
Type of a dict watcher callback function.
|
|
|
|
If *event* is ``PyDict_EVENT_CLEARED`` or ``PyDict_EVENT_DEALLOCATED``, both
|
|
*key* and *new_value* will be ``NULL``. If *event* is ``PyDict_EVENT_ADDED``
|
|
or ``PyDict_EVENT_MODIFIED``, *new_value* will be the new value for *key*.
|
|
If *event* is ``PyDict_EVENT_DELETED``, *key* is being deleted from the
|
|
dictionary and *new_value* will be ``NULL``.
|
|
|
|
``PyDict_EVENT_CLONED`` occurs when *dict* was previously empty and another
|
|
dict is merged into it. To maintain efficiency of this operation, per-key
|
|
``PyDict_EVENT_ADDED`` events are not issued in this case; instead a
|
|
single ``PyDict_EVENT_CLONED`` is issued, and *key* will be the source
|
|
dictionary.
|
|
|
|
The callback may inspect but must not modify *dict*; doing so could have
|
|
unpredictable effects, including infinite recursion. Do not trigger Python
|
|
code execution in the callback, as it could modify the dict as a side effect.
|
|
|
|
If *event* is ``PyDict_EVENT_DEALLOCATED``, taking a new reference in the
|
|
callback to the about-to-be-destroyed dictionary will resurrect it and
|
|
prevent it from being freed at this time. When the resurrected object is
|
|
destroyed later, any watcher callbacks active at that time will be called
|
|
again.
|
|
|
|
Callbacks occur before the notified modification to *dict* takes place, so
|
|
the prior state of *dict* can be inspected.
|
|
|
|
If the callback sets an exception, it must return ``-1``; this exception will
|
|
be printed as an unraisable exception using :c:func:`PyErr_WriteUnraisable`.
|
|
Otherwise it should return ``0``.
|
|
|
|
There may already be a pending exception set on entry to the callback. In
|
|
this case, the callback should return ``0`` with the same exception still
|
|
set. This means the callback may not call any other API that can set an
|
|
exception unless it saves and clears the exception state first, and restores
|
|
it before returning.
|
|
|
|
.. versionadded:: 3.12
|