cpython/Doc/library/ast.rst

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.. _ast:
Abstract Syntax Trees
=====================
.. module:: ast
:synopsis: Abstract Syntax Tree classes and manipulation.
.. sectionauthor:: Martin v. Löwis <martin@v.loewis.de>
.. sectionauthor:: Georg Brandl <georg@python.org>
.. versionadded:: 2.5
The low-level ``_ast`` module containing only the node classes.
.. versionadded:: 2.6
The high-level ``ast`` module containing all helpers.
The :mod:`ast` module helps Python applications to process trees of the Python
abstract syntax grammar. The abstract syntax itself might change with each
Python release; this module helps to find out programmatically what the current
grammar looks like.
Merged revisions 67154,67157-67159,67162-67163,67166,67175-67176,67189,67224-67225,67243 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r67154 | hirokazu.yamamoto | 2008-11-08 04:46:17 +0100 (Sat, 08 Nov 2008) | 1 line Issue #4071: ntpath.abspath returned an empty string for long unicode path. ........ r67157 | georg.brandl | 2008-11-08 12:47:44 +0100 (Sat, 08 Nov 2008) | 2 lines Don't use "HOWTO" as the title for all howto .tex files. ........ r67158 | georg.brandl | 2008-11-08 12:48:20 +0100 (Sat, 08 Nov 2008) | 2 lines Update "Documenting" a bit. Concentrate on Python-specifics. ........ r67159 | georg.brandl | 2008-11-08 13:52:25 +0100 (Sat, 08 Nov 2008) | 2 lines Fix warning. ........ r67162 | benjamin.peterson | 2008-11-08 17:55:33 +0100 (Sat, 08 Nov 2008) | 1 line a few compile() and ast doc improvements ........ r67163 | benjamin.peterson | 2008-11-08 18:04:18 +0100 (Sat, 08 Nov 2008) | 1 line move context clue to versionchanged tag ........ r67166 | benjamin.peterson | 2008-11-08 18:07:06 +0100 (Sat, 08 Nov 2008) | 1 line clarify what was added ........ r67175 | benjamin.peterson | 2008-11-09 02:44:32 +0100 (Sun, 09 Nov 2008) | 1 line update link ........ r67176 | benjamin.peterson | 2008-11-09 02:52:32 +0100 (Sun, 09 Nov 2008) | 1 line fix comment ........ r67189 | benjamin.peterson | 2008-11-11 22:56:06 +0100 (Tue, 11 Nov 2008) | 1 line use correct name ........ r67224 | georg.brandl | 2008-11-15 09:10:04 +0100 (Sat, 15 Nov 2008) | 2 lines #4324: fix getlocale() argument. ........ r67225 | brett.cannon | 2008-11-15 23:33:25 +0100 (Sat, 15 Nov 2008) | 1 line Clarify the docs for the 'strict' argument to httplib.HTTPConnection. ........ r67243 | benjamin.peterson | 2008-11-17 22:39:05 +0100 (Mon, 17 Nov 2008) | 1 line a few fixes on the download page ........
2008-12-05 04:35:09 -04:00
An abstract syntax tree can be generated by passing :data:`ast.PyCF_ONLY_AST` as
a flag to the :func:`compile` built-in function, or using the :func:`parse`
helper provided in this module. The result will be a tree of objects whose
Merged revisions 67154,67157-67159,67162-67163,67166,67175-67176,67189,67224-67225,67243 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r67154 | hirokazu.yamamoto | 2008-11-08 04:46:17 +0100 (Sat, 08 Nov 2008) | 1 line Issue #4071: ntpath.abspath returned an empty string for long unicode path. ........ r67157 | georg.brandl | 2008-11-08 12:47:44 +0100 (Sat, 08 Nov 2008) | 2 lines Don't use "HOWTO" as the title for all howto .tex files. ........ r67158 | georg.brandl | 2008-11-08 12:48:20 +0100 (Sat, 08 Nov 2008) | 2 lines Update "Documenting" a bit. Concentrate on Python-specifics. ........ r67159 | georg.brandl | 2008-11-08 13:52:25 +0100 (Sat, 08 Nov 2008) | 2 lines Fix warning. ........ r67162 | benjamin.peterson | 2008-11-08 17:55:33 +0100 (Sat, 08 Nov 2008) | 1 line a few compile() and ast doc improvements ........ r67163 | benjamin.peterson | 2008-11-08 18:04:18 +0100 (Sat, 08 Nov 2008) | 1 line move context clue to versionchanged tag ........ r67166 | benjamin.peterson | 2008-11-08 18:07:06 +0100 (Sat, 08 Nov 2008) | 1 line clarify what was added ........ r67175 | benjamin.peterson | 2008-11-09 02:44:32 +0100 (Sun, 09 Nov 2008) | 1 line update link ........ r67176 | benjamin.peterson | 2008-11-09 02:52:32 +0100 (Sun, 09 Nov 2008) | 1 line fix comment ........ r67189 | benjamin.peterson | 2008-11-11 22:56:06 +0100 (Tue, 11 Nov 2008) | 1 line use correct name ........ r67224 | georg.brandl | 2008-11-15 09:10:04 +0100 (Sat, 15 Nov 2008) | 2 lines #4324: fix getlocale() argument. ........ r67225 | brett.cannon | 2008-11-15 23:33:25 +0100 (Sat, 15 Nov 2008) | 1 line Clarify the docs for the 'strict' argument to httplib.HTTPConnection. ........ r67243 | benjamin.peterson | 2008-11-17 22:39:05 +0100 (Mon, 17 Nov 2008) | 1 line a few fixes on the download page ........
2008-12-05 04:35:09 -04:00
classes all inherit from :class:`ast.AST`. An abstract syntax tree can be
compiled into a Python code object using the built-in :func:`compile` function.
Node classes
------------
.. class:: AST
This is the base of all AST node classes. The actual node classes are
derived from the :file:`Parser/Python.asdl` file, which is reproduced
:ref:`below <abstract-grammar>`. They are defined in the :mod:`_ast` C
module and re-exported in :mod:`ast`.
There is one class defined for each left-hand side symbol in the abstract
grammar (for example, :class:`ast.stmt` or :class:`ast.expr`). In addition,
there is one class defined for each constructor on the right-hand side; these
classes inherit from the classes for the left-hand side trees. For example,
:class:`ast.BinOp` inherits from :class:`ast.expr`. For production rules
with alternatives (aka "sums"), the left-hand side class is abstract: only
instances of specific constructor nodes are ever created.
.. attribute:: _fields
Each concrete class has an attribute :attr:`_fields` which gives the names
of all child nodes.
Each instance of a concrete class has one attribute for each child node,
of the type as defined in the grammar. For example, :class:`ast.BinOp`
instances have an attribute :attr:`left` of type :class:`ast.expr`.
If these attributes are marked as optional in the grammar (using a
question mark), the value might be ``None``. If the attributes can have
zero-or-more values (marked with an asterisk), the values are represented
as Python lists. All possible attributes must be present and have valid
values when compiling an AST with :func:`compile`.
.. attribute:: lineno
col_offset
Instances of :class:`ast.expr` and :class:`ast.stmt` subclasses have
:attr:`lineno` and :attr:`col_offset` attributes. The :attr:`lineno` is
the line number of source text (1-indexed so the first line is line 1) and
the :attr:`col_offset` is the UTF-8 byte offset of the first token that
generated the node. The UTF-8 offset is recorded because the parser uses
UTF-8 internally.
The constructor of a class :class:`ast.T` parses its arguments as follows:
* If there are positional arguments, there must be as many as there are items
in :attr:`T._fields`; they will be assigned as attributes of these names.
* If there are keyword arguments, they will set the attributes of the same
names to the given values.
For example, to create and populate an :class:`ast.UnaryOp` node, you could
use ::
node = ast.UnaryOp()
node.op = ast.USub()
node.operand = ast.Num()
node.operand.n = 5
node.operand.lineno = 0
node.operand.col_offset = 0
node.lineno = 0
node.col_offset = 0
or the more compact ::
node = ast.UnaryOp(ast.USub(), ast.Num(5, lineno=0, col_offset=0),
lineno=0, col_offset=0)
2008-06-10 17:52:19 -03:00
.. versionadded:: 2.6
The constructor as explained above was added. In Python 2.5 nodes had
to be created by calling the class constructor without arguments and
setting the attributes afterwards.
.. _abstract-grammar:
Abstract Grammar
----------------
The module defines a string constant ``__version__`` which is the decimal
Subversion revision number of the file shown below.
The abstract grammar is currently defined as follows:
.. literalinclude:: ../../Parser/Python.asdl
:mod:`ast` Helpers
------------------
.. versionadded:: 2.6
Apart from the node classes, :mod:`ast` module defines these utility functions
and classes for traversing abstract syntax trees:
.. function:: parse(expr, filename='<unknown>', mode='exec')
Parse an expression into an AST node. Equivalent to ``compile(expr,
Merged revisions 67154,67157-67159,67162-67163,67166,67175-67176,67189,67224-67225,67243 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r67154 | hirokazu.yamamoto | 2008-11-08 04:46:17 +0100 (Sat, 08 Nov 2008) | 1 line Issue #4071: ntpath.abspath returned an empty string for long unicode path. ........ r67157 | georg.brandl | 2008-11-08 12:47:44 +0100 (Sat, 08 Nov 2008) | 2 lines Don't use "HOWTO" as the title for all howto .tex files. ........ r67158 | georg.brandl | 2008-11-08 12:48:20 +0100 (Sat, 08 Nov 2008) | 2 lines Update "Documenting" a bit. Concentrate on Python-specifics. ........ r67159 | georg.brandl | 2008-11-08 13:52:25 +0100 (Sat, 08 Nov 2008) | 2 lines Fix warning. ........ r67162 | benjamin.peterson | 2008-11-08 17:55:33 +0100 (Sat, 08 Nov 2008) | 1 line a few compile() and ast doc improvements ........ r67163 | benjamin.peterson | 2008-11-08 18:04:18 +0100 (Sat, 08 Nov 2008) | 1 line move context clue to versionchanged tag ........ r67166 | benjamin.peterson | 2008-11-08 18:07:06 +0100 (Sat, 08 Nov 2008) | 1 line clarify what was added ........ r67175 | benjamin.peterson | 2008-11-09 02:44:32 +0100 (Sun, 09 Nov 2008) | 1 line update link ........ r67176 | benjamin.peterson | 2008-11-09 02:52:32 +0100 (Sun, 09 Nov 2008) | 1 line fix comment ........ r67189 | benjamin.peterson | 2008-11-11 22:56:06 +0100 (Tue, 11 Nov 2008) | 1 line use correct name ........ r67224 | georg.brandl | 2008-11-15 09:10:04 +0100 (Sat, 15 Nov 2008) | 2 lines #4324: fix getlocale() argument. ........ r67225 | brett.cannon | 2008-11-15 23:33:25 +0100 (Sat, 15 Nov 2008) | 1 line Clarify the docs for the 'strict' argument to httplib.HTTPConnection. ........ r67243 | benjamin.peterson | 2008-11-17 22:39:05 +0100 (Mon, 17 Nov 2008) | 1 line a few fixes on the download page ........
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filename, mode, ast.PyCF_ONLY_AST)``.
Merged revisions 68133-68134,68141-68142,68145-68146,68148-68149,68159-68162,68166,68171-68174,68179,68195-68196,68210,68214-68215,68217-68222 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r68133 | antoine.pitrou | 2009-01-01 16:38:03 +0100 (Thu, 01 Jan 2009) | 1 line fill in actual issue number in tests ........ r68134 | hirokazu.yamamoto | 2009-01-01 16:45:39 +0100 (Thu, 01 Jan 2009) | 2 lines Issue #4797: IOError.filename was not set when _fileio.FileIO failed to open file with `str' filename on Windows. ........ r68141 | benjamin.peterson | 2009-01-01 17:43:12 +0100 (Thu, 01 Jan 2009) | 1 line fix highlighting ........ r68142 | benjamin.peterson | 2009-01-01 18:29:49 +0100 (Thu, 01 Jan 2009) | 2 lines welcome to 2009, Python! ........ r68145 | amaury.forgeotdarc | 2009-01-02 01:03:54 +0100 (Fri, 02 Jan 2009) | 5 lines #4801 _collections module fails to build on cygwin. _PyObject_GC_TRACK is the macro version of PyObject_GC_Track, and according to documentation it should not be used for extension modules. ........ r68146 | ronald.oussoren | 2009-01-02 11:44:46 +0100 (Fri, 02 Jan 2009) | 2 lines Fix for issue4472: "configure --enable-shared doesn't work on OSX" ........ r68148 | ronald.oussoren | 2009-01-02 11:48:31 +0100 (Fri, 02 Jan 2009) | 2 lines Forgot to add a NEWS item in my previous checkin ........ r68149 | ronald.oussoren | 2009-01-02 11:50:48 +0100 (Fri, 02 Jan 2009) | 2 lines Fix for issue4780 ........ r68159 | ronald.oussoren | 2009-01-02 15:48:17 +0100 (Fri, 02 Jan 2009) | 2 lines Fix for issue 1627952 ........ r68160 | ronald.oussoren | 2009-01-02 15:52:09 +0100 (Fri, 02 Jan 2009) | 2 lines Fix for issue r1737832 ........ r68161 | ronald.oussoren | 2009-01-02 16:00:05 +0100 (Fri, 02 Jan 2009) | 3 lines Fix for issue 1149804 ........ r68162 | ronald.oussoren | 2009-01-02 16:06:00 +0100 (Fri, 02 Jan 2009) | 3 lines Fix for issue 4472 is incompatible with Cygwin, this patch should fix that. ........ r68166 | benjamin.peterson | 2009-01-02 19:26:23 +0100 (Fri, 02 Jan 2009) | 1 line document PyMemberDef ........ r68171 | georg.brandl | 2009-01-02 21:25:14 +0100 (Fri, 02 Jan 2009) | 3 lines #4811: fix markup glitches (mostly remains of the conversion), found by Gabriel Genellina. ........ r68172 | martin.v.loewis | 2009-01-02 21:32:55 +0100 (Fri, 02 Jan 2009) | 2 lines Issue #4075: Use OutputDebugStringW in Py_FatalError. ........ r68173 | martin.v.loewis | 2009-01-02 21:40:14 +0100 (Fri, 02 Jan 2009) | 2 lines Issue #4051: Prevent conflict of UNICODE macros in cPickle. ........ r68174 | benjamin.peterson | 2009-01-02 21:47:27 +0100 (Fri, 02 Jan 2009) | 1 line fix compilation on non-Windows platforms ........ r68179 | raymond.hettinger | 2009-01-02 22:26:45 +0100 (Fri, 02 Jan 2009) | 1 line Issue #4615. Document how to use itertools for de-duping. ........ r68195 | georg.brandl | 2009-01-03 14:45:15 +0100 (Sat, 03 Jan 2009) | 2 lines Remove useless string literal. ........ r68196 | georg.brandl | 2009-01-03 15:29:53 +0100 (Sat, 03 Jan 2009) | 2 lines Fix indentation. ........ r68210 | georg.brandl | 2009-01-03 20:10:12 +0100 (Sat, 03 Jan 2009) | 2 lines Set eol-style correctly for mp_distributing.py. ........ r68214 | georg.brandl | 2009-01-03 20:44:48 +0100 (Sat, 03 Jan 2009) | 2 lines Make indentation consistent. ........ r68215 | georg.brandl | 2009-01-03 21:15:14 +0100 (Sat, 03 Jan 2009) | 2 lines Fix role name. ........ r68217 | georg.brandl | 2009-01-03 21:30:15 +0100 (Sat, 03 Jan 2009) | 2 lines Add rstlint, a little tool to find subtle markup problems and inconsistencies in the Doc sources. ........ r68218 | georg.brandl | 2009-01-03 21:38:59 +0100 (Sat, 03 Jan 2009) | 2 lines Recognize usage of the default role. ........ r68219 | georg.brandl | 2009-01-03 21:47:01 +0100 (Sat, 03 Jan 2009) | 2 lines Fix uses of the default role. ........ r68220 | georg.brandl | 2009-01-03 21:55:06 +0100 (Sat, 03 Jan 2009) | 2 lines Remove trailing whitespace. ........ r68221 | georg.brandl | 2009-01-03 22:04:55 +0100 (Sat, 03 Jan 2009) | 2 lines Remove tabs from the documentation. ........ r68222 | georg.brandl | 2009-01-03 22:11:58 +0100 (Sat, 03 Jan 2009) | 2 lines Disable the line length checker by default. ........
2009-01-03 17:55:17 -04:00
.. function:: literal_eval(node_or_string)
Safely evaluate an expression node or a string containing a Python
expression. The string or node provided may only consist of the following
Python literal structures: strings, numbers, tuples, lists, dicts, booleans,
and ``None``.
This can be used for safely evaluating strings containing Python expressions
from untrusted sources without the need to parse the values oneself.
.. function:: get_docstring(node, clean=True)
Return the docstring of the given *node* (which must be a
:class:`FunctionDef`, :class:`ClassDef` or :class:`Module` node), or ``None``
if it has no docstring. If *clean* is true, clean up the docstring's
indentation with :func:`inspect.cleandoc`.
.. function:: fix_missing_locations(node)
When you compile a node tree with :func:`compile`, the compiler expects
:attr:`lineno` and :attr:`col_offset` attributes for every node that supports
them. This is rather tedious to fill in for generated nodes, so this helper
adds these attributes recursively where not already set, by setting them to
the values of the parent node. It works recursively starting at *node*.
.. function:: increment_lineno(node, n=1)
Increment the line number of each node in the tree starting at *node* by *n*.
This is useful to "move code" to a different location in a file.
.. function:: copy_location(new_node, old_node)
Copy source location (:attr:`lineno` and :attr:`col_offset`) from *old_node*
to *new_node* if possible, and return *new_node*.
.. function:: iter_fields(node)
Yield a tuple of ``(fieldname, value)`` for each field in ``node._fields``
that is present on *node*.
.. function:: iter_child_nodes(node)
Yield all direct child nodes of *node*, that is, all fields that are nodes
and all items of fields that are lists of nodes.
.. function:: walk(node)
Recursively yield all child nodes of *node*, in no specified order. This is
useful if you only want to modify nodes in place and don't care about the
context.
.. class:: NodeVisitor()
A node visitor base class that walks the abstract syntax tree and calls a
visitor function for every node found. This function may return a value
Merged revisions 68133-68134,68141-68142,68145-68146,68148-68149,68159-68162,68166,68171-68174,68179,68195-68196,68210,68214-68215,68217-68222 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r68133 | antoine.pitrou | 2009-01-01 16:38:03 +0100 (Thu, 01 Jan 2009) | 1 line fill in actual issue number in tests ........ r68134 | hirokazu.yamamoto | 2009-01-01 16:45:39 +0100 (Thu, 01 Jan 2009) | 2 lines Issue #4797: IOError.filename was not set when _fileio.FileIO failed to open file with `str' filename on Windows. ........ r68141 | benjamin.peterson | 2009-01-01 17:43:12 +0100 (Thu, 01 Jan 2009) | 1 line fix highlighting ........ r68142 | benjamin.peterson | 2009-01-01 18:29:49 +0100 (Thu, 01 Jan 2009) | 2 lines welcome to 2009, Python! ........ r68145 | amaury.forgeotdarc | 2009-01-02 01:03:54 +0100 (Fri, 02 Jan 2009) | 5 lines #4801 _collections module fails to build on cygwin. _PyObject_GC_TRACK is the macro version of PyObject_GC_Track, and according to documentation it should not be used for extension modules. ........ r68146 | ronald.oussoren | 2009-01-02 11:44:46 +0100 (Fri, 02 Jan 2009) | 2 lines Fix for issue4472: "configure --enable-shared doesn't work on OSX" ........ r68148 | ronald.oussoren | 2009-01-02 11:48:31 +0100 (Fri, 02 Jan 2009) | 2 lines Forgot to add a NEWS item in my previous checkin ........ r68149 | ronald.oussoren | 2009-01-02 11:50:48 +0100 (Fri, 02 Jan 2009) | 2 lines Fix for issue4780 ........ r68159 | ronald.oussoren | 2009-01-02 15:48:17 +0100 (Fri, 02 Jan 2009) | 2 lines Fix for issue 1627952 ........ r68160 | ronald.oussoren | 2009-01-02 15:52:09 +0100 (Fri, 02 Jan 2009) | 2 lines Fix for issue r1737832 ........ r68161 | ronald.oussoren | 2009-01-02 16:00:05 +0100 (Fri, 02 Jan 2009) | 3 lines Fix for issue 1149804 ........ r68162 | ronald.oussoren | 2009-01-02 16:06:00 +0100 (Fri, 02 Jan 2009) | 3 lines Fix for issue 4472 is incompatible with Cygwin, this patch should fix that. ........ r68166 | benjamin.peterson | 2009-01-02 19:26:23 +0100 (Fri, 02 Jan 2009) | 1 line document PyMemberDef ........ r68171 | georg.brandl | 2009-01-02 21:25:14 +0100 (Fri, 02 Jan 2009) | 3 lines #4811: fix markup glitches (mostly remains of the conversion), found by Gabriel Genellina. ........ r68172 | martin.v.loewis | 2009-01-02 21:32:55 +0100 (Fri, 02 Jan 2009) | 2 lines Issue #4075: Use OutputDebugStringW in Py_FatalError. ........ r68173 | martin.v.loewis | 2009-01-02 21:40:14 +0100 (Fri, 02 Jan 2009) | 2 lines Issue #4051: Prevent conflict of UNICODE macros in cPickle. ........ r68174 | benjamin.peterson | 2009-01-02 21:47:27 +0100 (Fri, 02 Jan 2009) | 1 line fix compilation on non-Windows platforms ........ r68179 | raymond.hettinger | 2009-01-02 22:26:45 +0100 (Fri, 02 Jan 2009) | 1 line Issue #4615. Document how to use itertools for de-duping. ........ r68195 | georg.brandl | 2009-01-03 14:45:15 +0100 (Sat, 03 Jan 2009) | 2 lines Remove useless string literal. ........ r68196 | georg.brandl | 2009-01-03 15:29:53 +0100 (Sat, 03 Jan 2009) | 2 lines Fix indentation. ........ r68210 | georg.brandl | 2009-01-03 20:10:12 +0100 (Sat, 03 Jan 2009) | 2 lines Set eol-style correctly for mp_distributing.py. ........ r68214 | georg.brandl | 2009-01-03 20:44:48 +0100 (Sat, 03 Jan 2009) | 2 lines Make indentation consistent. ........ r68215 | georg.brandl | 2009-01-03 21:15:14 +0100 (Sat, 03 Jan 2009) | 2 lines Fix role name. ........ r68217 | georg.brandl | 2009-01-03 21:30:15 +0100 (Sat, 03 Jan 2009) | 2 lines Add rstlint, a little tool to find subtle markup problems and inconsistencies in the Doc sources. ........ r68218 | georg.brandl | 2009-01-03 21:38:59 +0100 (Sat, 03 Jan 2009) | 2 lines Recognize usage of the default role. ........ r68219 | georg.brandl | 2009-01-03 21:47:01 +0100 (Sat, 03 Jan 2009) | 2 lines Fix uses of the default role. ........ r68220 | georg.brandl | 2009-01-03 21:55:06 +0100 (Sat, 03 Jan 2009) | 2 lines Remove trailing whitespace. ........ r68221 | georg.brandl | 2009-01-03 22:04:55 +0100 (Sat, 03 Jan 2009) | 2 lines Remove tabs from the documentation. ........ r68222 | georg.brandl | 2009-01-03 22:11:58 +0100 (Sat, 03 Jan 2009) | 2 lines Disable the line length checker by default. ........
2009-01-03 17:55:17 -04:00
which is forwarded by the :meth:`visit` method.
This class is meant to be subclassed, with the subclass adding visitor
methods.
.. method:: visit(node)
Visit a node. The default implementation calls the method called
:samp:`self.visit_{classname}` where *classname* is the name of the node
class, or :meth:`generic_visit` if that method doesn't exist.
.. method:: generic_visit(node)
This visitor calls :meth:`visit` on all children of the node.
Merged revisions 68133-68134,68141-68142,68145-68146,68148-68149,68159-68162,68166,68171-68174,68179,68195-68196,68210,68214-68215,68217-68222 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r68133 | antoine.pitrou | 2009-01-01 16:38:03 +0100 (Thu, 01 Jan 2009) | 1 line fill in actual issue number in tests ........ r68134 | hirokazu.yamamoto | 2009-01-01 16:45:39 +0100 (Thu, 01 Jan 2009) | 2 lines Issue #4797: IOError.filename was not set when _fileio.FileIO failed to open file with `str' filename on Windows. ........ r68141 | benjamin.peterson | 2009-01-01 17:43:12 +0100 (Thu, 01 Jan 2009) | 1 line fix highlighting ........ r68142 | benjamin.peterson | 2009-01-01 18:29:49 +0100 (Thu, 01 Jan 2009) | 2 lines welcome to 2009, Python! ........ r68145 | amaury.forgeotdarc | 2009-01-02 01:03:54 +0100 (Fri, 02 Jan 2009) | 5 lines #4801 _collections module fails to build on cygwin. _PyObject_GC_TRACK is the macro version of PyObject_GC_Track, and according to documentation it should not be used for extension modules. ........ r68146 | ronald.oussoren | 2009-01-02 11:44:46 +0100 (Fri, 02 Jan 2009) | 2 lines Fix for issue4472: "configure --enable-shared doesn't work on OSX" ........ r68148 | ronald.oussoren | 2009-01-02 11:48:31 +0100 (Fri, 02 Jan 2009) | 2 lines Forgot to add a NEWS item in my previous checkin ........ r68149 | ronald.oussoren | 2009-01-02 11:50:48 +0100 (Fri, 02 Jan 2009) | 2 lines Fix for issue4780 ........ r68159 | ronald.oussoren | 2009-01-02 15:48:17 +0100 (Fri, 02 Jan 2009) | 2 lines Fix for issue 1627952 ........ r68160 | ronald.oussoren | 2009-01-02 15:52:09 +0100 (Fri, 02 Jan 2009) | 2 lines Fix for issue r1737832 ........ r68161 | ronald.oussoren | 2009-01-02 16:00:05 +0100 (Fri, 02 Jan 2009) | 3 lines Fix for issue 1149804 ........ r68162 | ronald.oussoren | 2009-01-02 16:06:00 +0100 (Fri, 02 Jan 2009) | 3 lines Fix for issue 4472 is incompatible with Cygwin, this patch should fix that. ........ r68166 | benjamin.peterson | 2009-01-02 19:26:23 +0100 (Fri, 02 Jan 2009) | 1 line document PyMemberDef ........ r68171 | georg.brandl | 2009-01-02 21:25:14 +0100 (Fri, 02 Jan 2009) | 3 lines #4811: fix markup glitches (mostly remains of the conversion), found by Gabriel Genellina. ........ r68172 | martin.v.loewis | 2009-01-02 21:32:55 +0100 (Fri, 02 Jan 2009) | 2 lines Issue #4075: Use OutputDebugStringW in Py_FatalError. ........ r68173 | martin.v.loewis | 2009-01-02 21:40:14 +0100 (Fri, 02 Jan 2009) | 2 lines Issue #4051: Prevent conflict of UNICODE macros in cPickle. ........ r68174 | benjamin.peterson | 2009-01-02 21:47:27 +0100 (Fri, 02 Jan 2009) | 1 line fix compilation on non-Windows platforms ........ r68179 | raymond.hettinger | 2009-01-02 22:26:45 +0100 (Fri, 02 Jan 2009) | 1 line Issue #4615. Document how to use itertools for de-duping. ........ r68195 | georg.brandl | 2009-01-03 14:45:15 +0100 (Sat, 03 Jan 2009) | 2 lines Remove useless string literal. ........ r68196 | georg.brandl | 2009-01-03 15:29:53 +0100 (Sat, 03 Jan 2009) | 2 lines Fix indentation. ........ r68210 | georg.brandl | 2009-01-03 20:10:12 +0100 (Sat, 03 Jan 2009) | 2 lines Set eol-style correctly for mp_distributing.py. ........ r68214 | georg.brandl | 2009-01-03 20:44:48 +0100 (Sat, 03 Jan 2009) | 2 lines Make indentation consistent. ........ r68215 | georg.brandl | 2009-01-03 21:15:14 +0100 (Sat, 03 Jan 2009) | 2 lines Fix role name. ........ r68217 | georg.brandl | 2009-01-03 21:30:15 +0100 (Sat, 03 Jan 2009) | 2 lines Add rstlint, a little tool to find subtle markup problems and inconsistencies in the Doc sources. ........ r68218 | georg.brandl | 2009-01-03 21:38:59 +0100 (Sat, 03 Jan 2009) | 2 lines Recognize usage of the default role. ........ r68219 | georg.brandl | 2009-01-03 21:47:01 +0100 (Sat, 03 Jan 2009) | 2 lines Fix uses of the default role. ........ r68220 | georg.brandl | 2009-01-03 21:55:06 +0100 (Sat, 03 Jan 2009) | 2 lines Remove trailing whitespace. ........ r68221 | georg.brandl | 2009-01-03 22:04:55 +0100 (Sat, 03 Jan 2009) | 2 lines Remove tabs from the documentation. ........ r68222 | georg.brandl | 2009-01-03 22:11:58 +0100 (Sat, 03 Jan 2009) | 2 lines Disable the line length checker by default. ........
2009-01-03 17:55:17 -04:00
Note that child nodes of nodes that have a custom visitor method won't be
visited unless the visitor calls :meth:`generic_visit` or visits them
itself.
Don't use the :class:`NodeVisitor` if you want to apply changes to nodes
during traversal. For this a special visitor exists
(:class:`NodeTransformer`) that allows modifications.
.. class:: NodeTransformer()
A :class:`NodeVisitor` subclass that walks the abstract syntax tree and
allows modification of nodes.
Merged revisions 68133-68134,68141-68142,68145-68146,68148-68149,68159-68162,68166,68171-68174,68179,68195-68196,68210,68214-68215,68217-68222 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r68133 | antoine.pitrou | 2009-01-01 16:38:03 +0100 (Thu, 01 Jan 2009) | 1 line fill in actual issue number in tests ........ r68134 | hirokazu.yamamoto | 2009-01-01 16:45:39 +0100 (Thu, 01 Jan 2009) | 2 lines Issue #4797: IOError.filename was not set when _fileio.FileIO failed to open file with `str' filename on Windows. ........ r68141 | benjamin.peterson | 2009-01-01 17:43:12 +0100 (Thu, 01 Jan 2009) | 1 line fix highlighting ........ r68142 | benjamin.peterson | 2009-01-01 18:29:49 +0100 (Thu, 01 Jan 2009) | 2 lines welcome to 2009, Python! ........ r68145 | amaury.forgeotdarc | 2009-01-02 01:03:54 +0100 (Fri, 02 Jan 2009) | 5 lines #4801 _collections module fails to build on cygwin. _PyObject_GC_TRACK is the macro version of PyObject_GC_Track, and according to documentation it should not be used for extension modules. ........ r68146 | ronald.oussoren | 2009-01-02 11:44:46 +0100 (Fri, 02 Jan 2009) | 2 lines Fix for issue4472: "configure --enable-shared doesn't work on OSX" ........ r68148 | ronald.oussoren | 2009-01-02 11:48:31 +0100 (Fri, 02 Jan 2009) | 2 lines Forgot to add a NEWS item in my previous checkin ........ r68149 | ronald.oussoren | 2009-01-02 11:50:48 +0100 (Fri, 02 Jan 2009) | 2 lines Fix for issue4780 ........ r68159 | ronald.oussoren | 2009-01-02 15:48:17 +0100 (Fri, 02 Jan 2009) | 2 lines Fix for issue 1627952 ........ r68160 | ronald.oussoren | 2009-01-02 15:52:09 +0100 (Fri, 02 Jan 2009) | 2 lines Fix for issue r1737832 ........ r68161 | ronald.oussoren | 2009-01-02 16:00:05 +0100 (Fri, 02 Jan 2009) | 3 lines Fix for issue 1149804 ........ r68162 | ronald.oussoren | 2009-01-02 16:06:00 +0100 (Fri, 02 Jan 2009) | 3 lines Fix for issue 4472 is incompatible with Cygwin, this patch should fix that. ........ r68166 | benjamin.peterson | 2009-01-02 19:26:23 +0100 (Fri, 02 Jan 2009) | 1 line document PyMemberDef ........ r68171 | georg.brandl | 2009-01-02 21:25:14 +0100 (Fri, 02 Jan 2009) | 3 lines #4811: fix markup glitches (mostly remains of the conversion), found by Gabriel Genellina. ........ r68172 | martin.v.loewis | 2009-01-02 21:32:55 +0100 (Fri, 02 Jan 2009) | 2 lines Issue #4075: Use OutputDebugStringW in Py_FatalError. ........ r68173 | martin.v.loewis | 2009-01-02 21:40:14 +0100 (Fri, 02 Jan 2009) | 2 lines Issue #4051: Prevent conflict of UNICODE macros in cPickle. ........ r68174 | benjamin.peterson | 2009-01-02 21:47:27 +0100 (Fri, 02 Jan 2009) | 1 line fix compilation on non-Windows platforms ........ r68179 | raymond.hettinger | 2009-01-02 22:26:45 +0100 (Fri, 02 Jan 2009) | 1 line Issue #4615. Document how to use itertools for de-duping. ........ r68195 | georg.brandl | 2009-01-03 14:45:15 +0100 (Sat, 03 Jan 2009) | 2 lines Remove useless string literal. ........ r68196 | georg.brandl | 2009-01-03 15:29:53 +0100 (Sat, 03 Jan 2009) | 2 lines Fix indentation. ........ r68210 | georg.brandl | 2009-01-03 20:10:12 +0100 (Sat, 03 Jan 2009) | 2 lines Set eol-style correctly for mp_distributing.py. ........ r68214 | georg.brandl | 2009-01-03 20:44:48 +0100 (Sat, 03 Jan 2009) | 2 lines Make indentation consistent. ........ r68215 | georg.brandl | 2009-01-03 21:15:14 +0100 (Sat, 03 Jan 2009) | 2 lines Fix role name. ........ r68217 | georg.brandl | 2009-01-03 21:30:15 +0100 (Sat, 03 Jan 2009) | 2 lines Add rstlint, a little tool to find subtle markup problems and inconsistencies in the Doc sources. ........ r68218 | georg.brandl | 2009-01-03 21:38:59 +0100 (Sat, 03 Jan 2009) | 2 lines Recognize usage of the default role. ........ r68219 | georg.brandl | 2009-01-03 21:47:01 +0100 (Sat, 03 Jan 2009) | 2 lines Fix uses of the default role. ........ r68220 | georg.brandl | 2009-01-03 21:55:06 +0100 (Sat, 03 Jan 2009) | 2 lines Remove trailing whitespace. ........ r68221 | georg.brandl | 2009-01-03 22:04:55 +0100 (Sat, 03 Jan 2009) | 2 lines Remove tabs from the documentation. ........ r68222 | georg.brandl | 2009-01-03 22:11:58 +0100 (Sat, 03 Jan 2009) | 2 lines Disable the line length checker by default. ........
2009-01-03 17:55:17 -04:00
The :class:`NodeTransformer` will walk the AST and use the return value of
the visitor methods to replace or remove the old node. If the return value
of the visitor method is ``None``, the node will be removed from its
location, otherwise it is replaced with the return value. The return value
may be the original node in which case no replacement takes place.
Here is an example transformer that rewrites all occurrences of name lookups
(``foo``) to ``data['foo']``::
class RewriteName(NodeTransformer):
def visit_Name(self, node):
return copy_location(Subscript(
value=Name(id='data', ctx=Load()),
slice=Index(value=Str(s=node.id)),
ctx=node.ctx
), node)
Keep in mind that if the node you're operating on has child nodes you must
either transform the child nodes yourself or call the :meth:`generic_visit`
method for the node first.
For nodes that were part of a collection of statements (that applies to all
statement nodes), the visitor may also return a list of nodes rather than
just a single node.
Usually you use the transformer like this::
node = YourTransformer().visit(node)
.. function:: dump(node, annotate_fields=True, include_attributes=False)
Return a formatted dump of the tree in *node*. This is mainly useful for
debugging purposes. The returned string will show the names and the values
for fields. This makes the code impossible to evaluate, so if evaluation is
wanted *annotate_fields* must be set to False. Attributes such as line
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numbers and column offsets are not dumped by default. If this is wanted,
*include_attributes* can be set to ``True``.