Patch #1810 by Thomas Lee, reviewed by myself:
allow compiling Python AST objects into code objects
in compile().
diff --git a/Doc/library/_ast.rst b/Doc/library/_ast.rst
index 9383591..e9f4ad4 100644
--- a/Doc/library/_ast.rst
+++ b/Doc/library/_ast.rst
@@ -12,16 +12,16 @@
.. versionadded:: 2.5
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 :term:`bytecode` 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.
+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 ``_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``.
+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
@@ -41,12 +41,15 @@
``_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.
+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.
+The constructors of all ``_ast`` classes don't take arguments; instead, if you
+create instances, you must assign the required attributes separately.
+
Abstract Grammar
----------------