"symtable" --- Access to the compiler's symbol tables
*****************************************************

**Source code:** Lib/symtable.py

======================================================================

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.  "symtable"
provides an interface to examine these tables.


Generating Symbol Tables
========================

symtable.symtable(code, filename, compile_type)

   Return the toplevel "SymbolTable" for the Python source *code*.
   *filename* is the name of the file containing the code.
   *compile_type* is like the *mode* argument to "compile()".


Examining Symbol Tables
=======================

class symtable.SymbolTable

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

   get_type()

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

   get_id()

      Return the table's identifier.

   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 ("get_type()"
      returns "'module'").

   get_lineno()

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

   is_optimized()

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

   is_nested()

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

   has_children()

      Return "True" if the block has nested namespaces within it.
      These can be obtained with "get_children()".

   get_identifiers()

      Return a list of names of symbols in this table.

   lookup(name)

      Lookup *name* in the table and return a "Symbol" instance.

   get_symbols()

      Return a list of "Symbol" instances for names in the table.

   get_children()

      Return a list of the nested symbol tables.

class symtable.Function

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

   get_parameters()

      Return a tuple containing names of parameters to this function.

   get_locals()

      Return a tuple containing names of locals in this function.

   get_globals()

      Return a tuple containing names of globals in this function.

   get_nonlocals()

      Return a tuple containing names of nonlocals in this function.

   get_frees()

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

class symtable.Class

   A namespace of a class.  This class inherits "SymbolTable".

   get_methods()

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

class symtable.Symbol

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

   get_name()

      Return the symbol's name.

   is_referenced()

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

   is_imported()

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

   is_parameter()

      Return "True" if the symbol is a parameter.

   is_global()

      Return "True" if the symbol is global.

   is_nonlocal()

      Return "True" if the symbol is nonlocal.

   is_declared_global()

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

   is_local()

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

   is_annotated()

      Return "True" if the symbol is annotated.

      3.6 版新加入.

   is_free()

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

   is_assigned()

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

   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.

      例如:

         >>> 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.

   get_namespaces()

      Return a list of namespaces bound to this name.

   get_namespace()

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