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Diffstat (limited to 'Doc/library/argparse.rst')
| -rw-r--r-- | Doc/library/argparse.rst | 54 |
1 files changed, 30 insertions, 24 deletions
diff --git a/Doc/library/argparse.rst b/Doc/library/argparse.rst index 29396c7a036..f189f6b8fa8 100644 --- a/Doc/library/argparse.rst +++ b/Doc/library/argparse.rst @@ -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 @@ -955,7 +943,7 @@ See also :ref:`specifying-ambiguous-arguments`. The supported values are: .. index:: single: + (plus); in argparse module -* ``'+'``. Just like ``'*'``, all command-line args present are gathered into a +* ``'+'``. Just like ``'*'``, all command-line arguments present are gathered into a list. Additionally, an error message will be generated if there wasn't at least one command-line argument present. For example:: @@ -1429,6 +1417,21 @@ 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 ----------------------- @@ -2122,12 +2125,15 @@ Partial parsing .. method:: ArgumentParser.parse_known_args(args=None, namespace=None) - Sometimes a script may only parse a few of the command-line arguments, passing - the remaining arguments on to another script or program. In these cases, the - :meth:`~ArgumentParser.parse_known_args` method can be useful. It works much like - :meth:`~ArgumentParser.parse_args` except that it does not produce an error when - extra arguments are present. Instead, it returns a two item tuple containing - the populated namespace and the list of remaining argument strings. + Sometimes a script only needs to handle a specific set of command-line + arguments, leaving any unrecognized arguments for another script or program. + In these cases, the :meth:`~ArgumentParser.parse_known_args` method can be + useful. + + This method works similarly to :meth:`~ArgumentParser.parse_args`, but it does + not raise an error for extra, unrecognized arguments. Instead, it parses the + known arguments and returns a two item tuple that contains the populated + namespace and the list of any unrecognized arguments. :: |