#?Author:?Steven?J.?Bethard?.

“““Command-line?parsing?library

This?module?is?an?optparse-inspired?command-line?parsing?library?that:

????-?handles?both?optional?and?positional?arguments
????-?produces?highly?informative?usage?messages
????-?supports?parsers?that?dispatch?to?sub-parsers

The?following?is?a?simple?usage?example?that?sums?integers?from?the
command-line?and?writes?the?result?to?a?file::

????parser?=?argparse.ArgumentParser（
????????description=‘sum?the?integers?at?the?command?line‘）
????parser.add_argument（
????????‘integers‘?metavar=‘int‘?nargs=‘+‘?type=int
????????help=‘an?integer?to?be?summed‘）
????parser.add_argument（
????????‘--log‘?default=sys.stdout?type=argparse.FileType（‘w‘）
????????help=‘the?file?where?the?sum?should?be?written‘）
????args?=?parser.parse_args（）
????args.log.write（‘%s‘?%?sum（args.integers））
????args.log.close（）

The?module?contains?the?following?public?classes:

????-?ArgumentParser?--?The?main?entry?point?for?command-line?parsing.?As?the
????????example?above?shows?the?add_argument（）?method?is?used?to?populate
????????the?parser?with?actions?for?optional?and?positional?arguments.?Then
????????the?parse_args（）?method?is?invoked?to?convert?the?args?at?the
????????command-line?into?an?object?with?attributes.

????-?ArgumentError?--?The?exception?raised?by?ArgumentParser?objects?when
????????there?are?errors?with?the?parser‘s?actions.?Errors?raised?while
????????parsing?the?command-line?are?caught?by?ArgumentParser?and?emitted
????????as?command-line?messages.

????-?FileType?--?A?factory?for?defining?types?of?files?to?be?created.?As?the
????????example?above?shows?instances?of?FileType?are?typically?passed?as
????????the?type=?argument?of?add_argument（）?calls.

????-?Action?--?The?base?class?for?parser?actions.?Typically?actions?are
????????selected?by?passing?strings?like?‘store_true‘?or?‘append_const‘?to
????????the?action=?argument?of?add_argument（）.?However?for?greater
????????customization?of?ArgumentParser?actions?subclasses?of?Action?may
????????be?defined?and?passed?as?the?action=?argument.

????-?HelpFormatter?RawDescriptionhelpFormatter?RawTextHelpFormatter
????????ArgumentDefaultsHelpFormatter?--?Formatter?classes?which
????????may?be?passed?as?the?formatter_class=?argument?to?the
????????ArgumentParser?constructor.?HelpFormatter?is?the?default
????????RawDescriptionhelpFormatter?and?RawTextHelpFormatter?tell?the?parser
????????not?to?change?the?formatting?for?help?text?and
????????ArgumentDefaultsHelpFormatter?adds?information?about?argument?defaults
????????to?the?help.

All?other?classes?in?this?module?are?considered?implementation?details.
（Also?note?that?HelpFormatter?and?RawDescriptionhelpFormatter?are?only
considered?public?as?object?names?--?the?API?of?the?formatter?objects?is
still?considered?an?implementation?detail.）
“““

__version__?=?‘1.2.1‘
__all__?=?[
????‘ArgumentParser‘
????‘ArgumentError‘
????‘ArgumentTypeError‘
????‘FileType‘
????‘H