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367 lines
9.9 KiB
ReStructuredText
367 lines
9.9 KiB
ReStructuredText
:mod:`!symtable` --- Access to the compiler's symbol tables
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===========================================================
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.. module:: symtable
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:synopsis: Interface to the compiler's internal symbol tables.
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**Source code:** :source:`Lib/symtable.py`
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--------------
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.. moduleauthor:: Jeremy Hylton <jeremy@alum.mit.edu>
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.. sectionauthor:: Benjamin Peterson <benjamin@python.org>
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Symbol tables are generated by the compiler from AST just before bytecode is
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generated. The symbol table is responsible for calculating the scope of every
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identifier in the code. :mod:`symtable` provides an interface to examine these
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tables.
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Generating Symbol Tables
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------------------------
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.. function:: symtable(code, filename, compile_type)
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Return the toplevel :class:`SymbolTable` for the Python source *code*.
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*filename* is the name of the file containing the code. *compile_type* is
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like the *mode* argument to :func:`compile`.
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Examining Symbol Tables
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-----------------------
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.. class:: SymbolTableType
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An enumeration indicating the type of a :class:`SymbolTable` object.
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.. attribute:: MODULE
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:value: "module"
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Used for the symbol table of a module.
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.. attribute:: FUNCTION
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:value: "function"
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Used for the symbol table of a function.
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.. attribute:: CLASS
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:value: "class"
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Used for the symbol table of a class.
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The following members refer to different flavors of
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:ref:`annotation scopes <annotation-scopes>`.
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.. attribute:: ANNOTATION
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:value: "annotation"
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Used for annotations if ``from __future__ import annotations`` is active.
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.. attribute:: TYPE_ALIAS
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:value: "type alias"
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Used for the symbol table of :keyword:`type` constructions.
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.. attribute:: TYPE_PARAMETERS
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:value: "type parameters"
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Used for the symbol table of :ref:`generic functions <generic-functions>`
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or :ref:`generic classes <generic-classes>`.
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.. attribute:: TYPE_VARIABLE
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:value: "type variable"
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Used for the symbol table of the bound, the constraint tuple or the
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default value of a single type variable in the formal sense, i.e.,
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a TypeVar, a TypeVarTuple or a ParamSpec object (the latter two do
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not support a bound or a constraint tuple).
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.. versionadded:: 3.13
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.. class:: SymbolTable
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A namespace table for a block. The constructor is not public.
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.. method:: get_type()
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Return the type of the symbol table. Possible values are members
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of the :class:`SymbolTableType` enumeration.
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.. versionchanged:: 3.12
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Added ``'annotation'``, ``'TypeVar bound'``, ``'type alias'``,
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and ``'type parameter'`` as possible return values.
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.. versionchanged:: 3.13
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Return values are members of the :class:`SymbolTableType` enumeration.
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The exact values of the returned string may change in the future,
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and thus, it is recommended to use :class:`SymbolTableType` members
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instead of hard-coded strings.
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.. method:: get_id()
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Return the table's identifier.
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.. method:: get_name()
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Return the table's name. This is the name of the class if the table is
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for a class, the name of the function if the table is for a function, or
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``'top'`` if the table is global (:meth:`get_type` returns ``'module'``).
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For type parameter scopes (which are used for generic classes, functions,
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and type aliases), it is the name of the underlying class, function, or
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type alias. For type alias scopes, it is the name of the type alias.
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For :class:`~typing.TypeVar` bound scopes, it is the name of the ``TypeVar``.
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.. method:: get_lineno()
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Return the number of the first line in the block this table represents.
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.. method:: is_optimized()
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Return ``True`` if the locals in this table can be optimized.
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.. method:: is_nested()
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Return ``True`` if the block is a nested class or function.
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.. method:: has_children()
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Return ``True`` if the block has nested namespaces within it. These can
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be obtained with :meth:`get_children`.
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.. method:: get_identifiers()
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Return a view object containing the names of symbols in the table.
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See the :ref:`documentation of view objects <dict-views>`.
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.. method:: lookup(name)
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Lookup *name* in the table and return a :class:`Symbol` instance.
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.. method:: get_symbols()
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Return a list of :class:`Symbol` instances for names in the table.
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.. method:: get_children()
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Return a list of the nested symbol tables.
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.. class:: Function
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A namespace for a function or method. This class inherits from
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:class:`SymbolTable`.
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.. method:: get_parameters()
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Return a tuple containing names of parameters to this function.
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.. method:: get_locals()
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Return a tuple containing names of locals in this function.
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.. method:: get_globals()
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Return a tuple containing names of globals in this function.
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.. method:: get_nonlocals()
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Return a tuple containing names of explicitly declared nonlocals in this function.
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.. method:: get_frees()
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Return a tuple containing names of :term:`free (closure) variables <closure variable>`
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in this function.
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.. class:: Class
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A namespace of a class. This class inherits from :class:`SymbolTable`.
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.. method:: get_methods()
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Return a tuple containing the names of method-like functions declared
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in the class.
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Here, the term 'method' designates *any* function defined in the class
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body via :keyword:`def` or :keyword:`async def`.
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Functions defined in a deeper scope (e.g., in an inner class) are not
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picked up by :meth:`get_methods`.
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For example:
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.. testsetup:: symtable.Class.get_methods
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import warnings
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context = warnings.catch_warnings()
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context.__enter__()
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warnings.simplefilter("ignore", category=DeprecationWarning)
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.. testcleanup:: symtable.Class.get_methods
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context.__exit__()
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.. doctest:: symtable.Class.get_methods
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>>> import symtable
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>>> st = symtable.symtable('''
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... def outer(): pass
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...
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... class A:
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... def f():
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... def w(): pass
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...
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... def g(self): pass
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...
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... @classmethod
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... async def h(cls): pass
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...
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... global outer
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... def outer(self): pass
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... ''', 'test', 'exec')
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>>> class_A = st.get_children()[2]
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>>> class_A.get_methods()
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('f', 'g', 'h')
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Although ``A().f()`` raises :exc:`TypeError` at runtime, ``A.f`` is still
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considered as a method-like function.
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.. deprecated-removed:: 3.14 3.16
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.. class:: Symbol
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An entry in a :class:`SymbolTable` corresponding to an identifier in the
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source. The constructor is not public.
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.. method:: get_name()
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Return the symbol's name.
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.. method:: is_referenced()
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Return ``True`` if the symbol is used in its block.
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.. method:: is_imported()
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Return ``True`` if the symbol is created from an import statement.
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.. method:: is_parameter()
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Return ``True`` if the symbol is a parameter.
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.. method:: is_type_parameter()
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Return ``True`` if the symbol is a type parameter.
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.. versionadded:: 3.14
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.. method:: is_global()
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Return ``True`` if the symbol is global.
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.. method:: is_nonlocal()
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Return ``True`` if the symbol is nonlocal.
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.. method:: is_declared_global()
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Return ``True`` if the symbol is declared global with a global statement.
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.. method:: is_local()
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Return ``True`` if the symbol is local to its block.
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.. method:: is_annotated()
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Return ``True`` if the symbol is annotated.
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.. versionadded:: 3.6
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.. method:: is_free()
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Return ``True`` if the symbol is referenced in its block, but not assigned
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to.
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.. method:: is_free_class()
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Return *True* if a class-scoped symbol is free from
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the perspective of a method.
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Consider the following example::
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def f():
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x = 1 # function-scoped
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class C:
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x = 2 # class-scoped
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def method(self):
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return x
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In this example, the class-scoped symbol ``x`` is considered to
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be free from the perspective of ``C.method``, thereby allowing
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the latter to return *1* at runtime and not *2*.
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.. versionadded:: 3.14
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.. method:: is_assigned()
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Return ``True`` if the symbol is assigned to in its block.
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.. method:: is_comp_iter()
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Return ``True`` if the symbol is a comprehension iteration variable.
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.. versionadded:: 3.14
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.. method:: is_comp_cell()
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Return ``True`` if the symbol is a cell in an inlined comprehension.
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.. versionadded:: 3.14
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.. method:: is_namespace()
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Return ``True`` if name binding introduces new namespace.
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If the name is used as the target of a function or class statement, this
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will be true.
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For example::
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>>> table = symtable.symtable("def some_func(): pass", "string", "exec")
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>>> table.lookup("some_func").is_namespace()
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True
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Note that a single name can be bound to multiple objects. If the result
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is ``True``, the name may also be bound to other objects, like an int or
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list, that does not introduce a new namespace.
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.. method:: get_namespaces()
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Return a list of namespaces bound to this name.
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.. method:: get_namespace()
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Return the namespace bound to this name. If more than one or no namespace
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is bound to this name, a :exc:`ValueError` is raised.
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.. _symtable-cli:
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Command-Line Usage
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------------------
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.. versionadded:: 3.13
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The :mod:`symtable` module can be executed as a script from the command line.
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.. code-block:: sh
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python -m symtable [infile...]
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Symbol tables are generated for the specified Python source files and
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dumped to stdout.
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If no input file is specified, the content is read from stdin.
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