example-argparse.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
argparse sample code
~~~~~~~~~~~~~~~~~~~~

Not the complete list of add_argument parameters, just the most common
----------------------------------------------------------------------

arg name or optional flags:
    positional (required option): "foo"
    options:  "-f", "--foo"

action=<keyword>
    * store_true: Special case of const, sets flag to True when flag is found.
    * store_true: Special case of const, sets flag to False when flag is found.
    * store_const: Used with an optional flag to assign a value when set.
    * append_const: store each constant set by specified flags in a list
    * append: allows option multiple times, stores values in a list

nargs: The number of command-line arguments to consume.
  <int>: Specified value.
    '?': Zero or One.
    '*': Zero or more.
    '+': One or more.

default=<value>
    Default value is option is omitted.

type=<type>
    Convert the arg string to a specified Python <type>.

choices=[item1, item2, ...]
    Arg value must appear in the specified list.

help='<description>'
    Brief description of what the argument does.

dest='<name>'
    Name of the attribute to store the result in.

metavar='<name>'
    Name of the argument when included in usage messages.

References:
    * Primary Reference: https://docs.python.org/dev/library/argparse.html#prog
    * Original forked from: https://gist.github.com/fabiantheblind/5916265
    * Added some docstring info from: https://gist.github.com/dsc/3855240
    * For a more advanced example of a custom action (not included here) visit
      https://gist.github.com/brantfaircloth/1443543
"""

__version__ = '0.1'
__license__ = '''

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.'''


import argparse
import sys
from pprint import pprint


class CustomAction(argparse.Action):
    def __call__(self, parser, namespace, values, option_string=None):
        print('%r %r %r' % (namespace, values, option_string))
        setattr(namespace, self.dest, values)


def main(args):
    pprint(args)


if __name__ == '__main__':

    # explicitly setting prog & usage to demo default settings
    boilerplate_parser = argparse.ArgumentParser(
        add_help=False,
        prog=sys.argv[0],
        usage='%(prog)s [options]',
        description='Demonstration of argparse')

    boilerplate_parser.add_argument(
        '--version',
        action='version',
        version='%(prog)s ' + __version__ + __license__)

    # inherits common base (parent) parser ...
    # add_help=False in the parent's parameters is required for this to work
    # overrides epilog
    # formatter_class:
    #   RawDescriptionHelpFormatter: desc & epilog should displayed as-is
    #   RawTextHelpFormatter:  maintains whitespace for help & arg descriptions
    #   ArgumentDefaultsHelpFormatter: adds default values to arg help messages
    #   MetavarTypeHelpFormatter:  uses name of type arg for each argument
    #       as the display name for its values (rather than dest):
    epilog = '''this epilog description indenting is messed up to demo
        raw formatting'''
    parser = argparse.ArgumentParser(parents=[boilerplate_parser],
        epilog=epilog, formatter_class=argparse.RawDescriptionHelpFormatter)

    parser.add_argument('-f', '--flag', action='store_true',
                        help='optional flag, True when specfied else False')

    parser.add_argument('--integer', type=int, dest='number',
                        help='an integer')

    parser.add_argument('--choice', choices=['one', 'two', 'three'],
                        help='chose one, two or three')

    parser.add_argument('--int_choice', type=int, choices=[1, 2, 3],
                        help='chose a number from 1 to 3')

    #parser.parse_args('--foo=FOO'.split())

    parser.add_argument('--custom', action=CustomAction)

    parser.add_argument('required', help='required positional arg')

    parser.add_argument('filenames', nargs='*',
                        help='zero or more positional args')
    
    args = parser.parse_args()
    main(args)