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:mod:`symtable` --- Access to the compiler's symbol tables

.. module:: symtable
   :synopsis: Interface to the compiler's internal symbol tables.

Source code: :source:`Lib/symtable.py`

.. moduleauthor:: Jeremy Hylton <jeremy@alum.mit.edu>

.. sectionauthor:: Benjamin Peterson <benjamin@python.org>

Symbol tables are generated by the compiler from AST just before bytecode is generated. The symbol table is responsible for calculating the scope of every identifier in the code. :mod:`symtable` provides an interface to examine these tables.

Generating Symbol Tables

.. function:: symtable(code, filename, compile_type)

   Return the toplevel :class:`SymbolTable` for the Python source *code*.
   *filename* is the name of the file containing the code.  *compile_type* is
   like the *mode* argument to :func:`compile`.

Examining Symbol Tables

A namespace table for a block. The constructor is not public.

.. method:: get_type()

   Return the type of the symbol table.  Possible values are ``'class'``,
   ``'module'``, and ``'function'``.


.. method:: get_id()

   Return the table's identifier.


.. method:: get_name()

   Return the table's name.  This is the name of the class if the table is
   for a class, the name of the function if the table is for a function, or
   ``'top'`` if the table is global (:meth:`get_type` returns ``'module'``).


.. method:: get_lineno()

   Return the number of the first line in the block this table represents.


.. method:: is_optimized()

   Return ``True`` if the locals in this table can be optimized.


.. method:: is_nested()

   Return ``True`` if the block is a nested class or function.


.. method:: has_children()

   Return ``True`` if the block has nested namespaces within it.  These can
   be obtained with :meth:`get_children`.


.. method:: has_exec()

   Return ``True`` if the block uses ``exec``.


.. method:: get_identifiers()

   Return a list of names of symbols in this table.


.. method:: lookup(name)

   Lookup *name* in the table and return a :class:`Symbol` instance.


.. method:: get_symbols()

   Return a list of :class:`Symbol` instances for names in the table.


.. method:: get_children()

   Return a list of the nested symbol tables.

A namespace for a function or method. This class inherits :class:`SymbolTable`.

.. method:: get_parameters()

   Return a tuple containing names of parameters to this function.


.. method:: get_locals()

   Return a tuple containing names of locals in this function.


.. method:: get_globals()

   Return a tuple containing names of globals in this function.


.. method:: get_frees()

   Return a tuple containing names of free variables in this function.

A namespace of a class. This class inherits :class:`SymbolTable`.

.. method:: get_methods()

   Return a tuple containing the names of methods declared in the class.

An entry in a :class:`SymbolTable` corresponding to an identifier in the source. The constructor is not public.

.. method:: get_name()

   Return the symbol's name.


.. method:: is_referenced()

   Return ``True`` if the symbol is used in its block.


.. method:: is_imported()

   Return ``True`` if the symbol is created from an import statement.


.. method:: is_parameter()

   Return ``True`` if the symbol is a parameter.


.. method:: is_global()

   Return ``True`` if the symbol is global.


.. method:: is_declared_global()

   Return ``True`` if the symbol is declared global with a global statement.


.. method:: is_local()

   Return ``True`` if the symbol is local to its block.


.. method:: is_free()

   Return ``True`` if the symbol is referenced in its block, but not assigned
   to.


.. method:: is_assigned()

   Return ``True`` if the symbol is assigned to in its block.


.. method:: is_namespace()

   Return ``True`` if name binding introduces new namespace.

   If the name is used as the target of a function or class statement, this
   will be true.

   For example::

      >>> table = symtable.symtable("def some_func(): pass", "string", "exec")
      >>> table.lookup("some_func").is_namespace()
      True

   Note that a single name can be bound to multiple objects.  If the result
   is ``True``, the name may also be bound to other objects, like an int or
   list, that does not introduce a new namespace.


.. method:: get_namespaces()

   Return a list of namespaces bound to this name.


.. method:: get_namespace()

   Return the namespace bound to this name.  If more than one namespace is
   bound, :exc:`ValueError` is raised.