--- rest25/library/ast.rst	2008-12-19 16:58:07.000000000 +0900
+++ rest262/library/ast.rst	2009-04-05 05:02:09.000000000 +0900
@@ -1,62 +1,261 @@
-.. % XXX Label can't be _ast?
-.. % XXX Where should this section/chapter go?
-
-
 .. _ast:
 
-*********************
 Abstract Syntax Trees
-*********************
+=====================
 
-.. sectionauthor:: Martin v. Löwis <martin@v.loewis.de>
+.. 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.
+
+An abstract syntax tree can be generated by passing :data:`ast.PyCF_ONLY_AST` as
+a flag to the :func:`compile` builtin function, or using the :func:`parse`
+helper provided in this module.  The result will be a tree of objects whose
+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:
 
-The ``_ast`` module helps Python applications to process trees of the Python
-abstract syntax grammar. The Python compiler currently provides read-only access
-to such trees, meaning that applications can only create a tree for a given
-piece of Python source code; generating byte code from a (potentially modified)
-tree is not supported. The abstract syntax itself might change with each Python
-release; this module helps to find out programmatically what the current grammar
-looks like.
-
-An abstract syntax tree can be generated by passing ``_ast.PyCF_ONLY_AST`` as a
-flag to the :func:`compile` builtin function. The result will be a tree of
-objects whose classes all inherit from ``_ast.AST``.
-
-The actual classes are derived from the ``Parser/Python.asdl`` file, which is
-reproduced below. There is one class defined for each left-hand side symbol in
-the abstract grammar (for example, ``_ast.stmt`` or ``_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,
-``_ast.BinOp`` inherits from ``_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.
-
-Each concrete class has an attribute ``_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, ``_ast.BinOp`` instances have an
-attribute ``left`` of type ``_ast.expr``.   Instances of ``_ast.expr`` and
-``_ast.stmt`` subclasses also have lineno and col_offset attributes.  The lineno
-is the line number of source text (1 indexed so the first line is line 1) and
-the col_offset is the utf8 byte offset of the first token that generated the
-node.  The utf8 offset is recorded because the parser uses utf8  internally.
-
-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.
+   * 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)
+
+   .. 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.
+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,
+   filename, mode, ast.PyCF_ONLY_AST)``.
+
+
+.. 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
+   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.
+
+      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.
+
+   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)
 
-.. XXX includefile ../../Parser/Python.asdl
+   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
+   numbers and column offsets are not dumped by default.  If this is wanted,
+   *include_attributes* can be set to ``True``.
