1:mod:`symtable` --- Access to the compiler's symbol tables
2==========================================================
3
4.. module:: symtable
5   :synopsis: Interface to the compiler's internal symbol tables.
6
7**Source code:** :source:`Lib/symtable.py`
8
9--------------
10
11.. moduleauthor:: Jeremy Hylton <[email protected]>
12.. sectionauthor:: Benjamin Peterson <[email protected]>
13
14
15Symbol tables are generated by the compiler from AST just before bytecode is
16generated.  The symbol table is responsible for calculating the scope of every
17identifier in the code.  :mod:`symtable` provides an interface to examine these
18tables.
19
20
21Generating Symbol Tables
22------------------------
23
24.. function:: symtable(code, filename, compile_type)
25
26   Return the toplevel :class:`SymbolTable` for the Python source *code*.
27   *filename* is the name of the file containing the code.  *compile_type* is
28   like the *mode* argument to :func:`compile`.
29
30
31Examining Symbol Tables
32-----------------------
33
34.. class:: SymbolTable
35
36   A namespace table for a block.  The constructor is not public.
37
38   .. method:: get_type()
39
40      Return the type of the symbol table.  Possible values are ``'class'``,
41      ``'module'``, and ``'function'``.
42
43   .. method:: get_id()
44
45      Return the table's identifier.
46
47   .. method:: get_name()
48
49      Return the table's name.  This is the name of the class if the table is
50      for a class, the name of the function if the table is for a function, or
51      ``'top'`` if the table is global (:meth:`get_type` returns ``'module'``).
52
53   .. method:: get_lineno()
54
55      Return the number of the first line in the block this table represents.
56
57   .. method:: is_optimized()
58
59      Return ``True`` if the locals in this table can be optimized.
60
61   .. method:: is_nested()
62
63      Return ``True`` if the block is a nested class or function.
64
65   .. method:: has_children()
66
67      Return ``True`` if the block has nested namespaces within it.  These can
68      be obtained with :meth:`get_children`.
69
70   .. method:: has_exec()
71
72      Return ``True`` if the block uses ``exec``.
73
74   .. method:: has_import_star()
75
76      Return ``True`` if the block uses a starred from-import.
77
78   .. method:: get_identifiers()
79
80      Return a list of names of symbols in this table.
81
82   .. method:: lookup(name)
83
84      Lookup *name* in the table and return a :class:`Symbol` instance.
85
86   .. method:: get_symbols()
87
88      Return a list of :class:`Symbol` instances for names in the table.
89
90   .. method:: get_children()
91
92      Return a list of the nested symbol tables.
93
94
95.. class:: Function
96
97   A namespace for a function or method.  This class inherits
98   :class:`SymbolTable`.
99
100   .. method:: get_parameters()
101
102      Return a tuple containing names of parameters to this function.
103
104   .. method:: get_locals()
105
106      Return a tuple containing names of locals in this function.
107
108   .. method:: get_globals()
109
110      Return a tuple containing names of globals in this function.
111
112   .. method:: get_frees()
113
114      Return a tuple containing names of free variables in this function.
115
116
117.. class:: Class
118
119   A namespace of a class.  This class inherits :class:`SymbolTable`.
120
121   .. method:: get_methods()
122
123      Return a tuple containing the names of methods declared in the class.
124
125
126.. class:: Symbol
127
128   An entry in a :class:`SymbolTable` corresponding to an identifier in the
129   source.  The constructor is not public.
130
131   .. method:: get_name()
132
133      Return the symbol's name.
134
135   .. method:: is_referenced()
136
137      Return ``True`` if the symbol is used in its block.
138
139   .. method:: is_imported()
140
141      Return ``True`` if the symbol is created from an import statement.
142
143   .. method:: is_parameter()
144
145      Return ``True`` if the symbol is a parameter.
146
147   .. method:: is_global()
148
149      Return ``True`` if the symbol is global.
150
151   .. method:: is_declared_global()
152
153      Return ``True`` if the symbol is declared global with a global statement.
154
155   .. method:: is_local()
156
157      Return ``True`` if the symbol is local to its block.
158
159   .. method:: is_free()
160
161      Return ``True`` if the symbol is referenced in its block, but not assigned
162      to.
163
164   .. method:: is_assigned()
165
166      Return ``True`` if the symbol is assigned to in its block.
167
168   .. method:: is_namespace()
169
170      Return ``True`` if name binding introduces new namespace.
171
172      If the name is used as the target of a function or class statement, this
173      will be true.
174
175      For example::
176
177         >>> table = symtable.symtable("def some_func(): pass", "string", "exec")
178         >>> table.lookup("some_func").is_namespace()
179         True
180
181      Note that a single name can be bound to multiple objects.  If the result
182      is ``True``, the name may also be bound to other objects, like an int or
183      list, that does not introduce a new namespace.
184
185   .. method:: get_namespaces()
186
187      Return a list of namespaces bound to this name.
188
189   .. method:: get_namespace()
190
191      Return the namespace bound to this name.  If more than one namespace is
192      bound, a :exc:`ValueError` is raised.
193