bpo-38049: Add command-line interface for the ast module. (GH-15724)

Author: serhiy-storchaka

Doc/library/ast.rst

@@ -340,6 +340,42 @@ and classes for traversing abstract syntax trees:
  Added the *indent* option.
 
 
+.. _ast-cli:
+
+Command-Line Usage
+------------------
+
+.. versionadded:: 3.9
+
+The :mod:`ast` module can be executed as a script from the command line.
+It is as simple as:
+
+.. code-block:: sh
+
+ python -m ast [-m <mode>] [-a] [infile]
+
+The following options are accepted:
+
+.. program:: ast
+
+.. cmdoption:: -h, --help
+
+ Show the help message and exit.
+
+.. cmdoption:: -m <mode>
+ --mode <mode>
+
+ Specify what kind of code must be compiled, like the *mode* argument
+ in :func:`parse`.
+
+.. cmdoption:: -a, --include-attributes
+
+ Include attributes such as line numbers and column offsets.
+
+If :file:`infile` is specified its contents are parsed to AST and dumped
+to stdout. Otherwise, the content is read from stdin.
+
+
 .. seealso::
 
  `Green Tree Snakes <https://greentreesnakes.readthedocs.io/>`_, an external documentation resource, has good

Lib/ast.py

@@ -550,3 +550,27 @@ def __new__(cls, *args, **kwargs):
  bytes: 'Bytes',
  type(...): 'Ellipsis',
 }
+
+
+def main():
+ import argparse
+
+ parser = argparse.ArgumentParser(prog='python -m ast')
+ parser.add_argument('infile', type=argparse.FileType(mode='rb'), nargs='?',
+ default='-',
+ help='the file to parse; defaults to stdin')
+ parser.add_argument('-m', '--mode', default='exec',
+ choices=('exec', 'single', 'eval', 'func_type'),
+ help='specify what kind of code must be parsed')
+ parser.add_argument('-a', '--include-attributes', action='store_true',
+ help='include attributes such as line numbers and '
+ 'column offsets')
+ args = parser.parse_args()
+
+ with args.infile as infile:
+ source = infile.read()
+ tree = parse(source, args.infile.name, args.mode, type_comments=True)
+ print(dump(tree, include_attributes=args.include_attributes, indent=3))
+
+if __name__ == '__main__':
+ main()

Misc/NEWS.d/next/Library/2019-09-07-12-32-50.bpo-38049.xKP4tf.rst

@@ -0,0 +1 @@
+Added command-line interface for the :mod:`ast` module.