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36 changes: 19 additions & 17 deletions Doc/library/argparse.rst
Original file line number Diff line number Diff line change
Expand Up @@ -839,23 +839,11 @@ how the command-line arguments should be handled. The supplied actions are:
>>> parser.parse_args(['--version'])
PROG 2.0

Only actions that consume command-line arguments (e.g. ``'store'``,
``'append'`` or ``'extend'``) can be used with positional arguments.

.. class:: BooleanOptionalAction

You may also specify an arbitrary action by passing an :class:`Action` subclass or
other object that implements the same interface. The :class:`!BooleanOptionalAction`
is available in :mod:`!argparse` and adds support for boolean actions such as
``--foo`` and ``--no-foo``::

>>> import argparse
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', action=argparse.BooleanOptionalAction)
>>> parser.parse_args(['--no-foo'])
Namespace(foo=False)

.. versionadded:: 3.9
You may also specify an arbitrary action by passing an :class:`Action` subclass
(e.g. :class:`BooleanOptionalAction`) or other object that implements the same
interface. Only actions that consume command-line arguments (e.g. ``'store'``,
``'append'``, ``'extend'``, or custom actions with non-zero ``nargs``) can be used
with positional arguments.

The recommended way to create a custom action is to extend :class:`Action`,
overriding the :meth:`!__call__` method and optionally the :meth:`!__init__` and
Expand Down Expand Up @@ -1429,6 +1417,20 @@ this API may be passed as the ``action`` parameter to
and return a string which will be used when printing the usage of the program.
If such method is not provided, a sensible default will be used.

.. class:: BooleanOptionalAction

A subclass of :class:`Action` for handling boolean flags with positive
and negative options. Adding a single argument such as ``--foo`` automatically
creates both ``--foo`` and ``--no-foo`` options, storing ``True`` and ``False``
respectively::

>>> import argparse
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', action=argparse.BooleanOptionalAction)
>>> parser.parse_args(['--no-foo'])
Namespace(foo=False)

.. versionadded:: 3.9

The parse_args() method
-----------------------
Expand Down
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