Add the "ast" module, containing helpers to ease use of the "_ast" classes.
diff --git a/Doc/ACKS.txt b/Doc/ACKS.txt
index 337a57a..84d7339 100644
--- a/Doc/ACKS.txt
+++ b/Doc/ACKS.txt
@@ -157,6 +157,7 @@
* Bernhard Reiter
* Armin Rigo
* Wes Rishel
+ * Armin Ronacher
* Jim Roskind
* Guido van Rossum
* Donald Wallace Rouse II
diff --git a/Doc/library/_ast.rst b/Doc/library/_ast.rst
deleted file mode 100644
index c123d0a..0000000
--- a/Doc/library/_ast.rst
+++ /dev/null
@@ -1,85 +0,0 @@
-.. _ast:
-
-Abstract Syntax Trees
-=====================
-
-.. module:: _ast
- :synopsis: Abstract Syntax Tree classes.
-
-.. sectionauthor:: Martin v. Löwis <martin@v.loewis.de>
-
-
-.. versionadded:: 2.5
-
-The ``_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. The result will be a tree of
-objects whose classes all inherit from :class:`_ast.AST`.
-
-A modified abstract syntax tree can be compiled into a Python code object using
-the built-in :func:`compile` function.
-
-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.
-All possible attributes must be present and have valid values when compiling an
-AST with :func:`compile`.
-
-The constructor of a class ``_ast.T`` parses their arguments as follows:
-
-* If there are positional arguments, there must be as many as there are items in
- ``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 a ``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)
-
-
-
-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
diff --git a/Doc/library/ast.rst b/Doc/library/ast.rst
new file mode 100644
index 0000000..70840da
--- /dev/null
+++ b/Doc/library/ast.rst
@@ -0,0 +1,257 @@
+.. _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.
+
+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`.
+
+A modified 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)
+
+
+.. _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,
+ filename, mode, 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 `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 `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
+ numbers and column offsets are dumped by default. If this is wanted,
+ *include_attributes* can be set to ``True``.
diff --git a/Doc/library/language.rst b/Doc/library/language.rst
index 7d6af7d..bcf9ac0 100644
--- a/Doc/library/language.rst
+++ b/Doc/library/language.rst
@@ -15,7 +15,7 @@
.. toctree::
parser.rst
- _ast.rst
+ ast.rst
symbol.rst
token.rst
keyword.rst