#!/usr/bin/env python3

import argparse

# sub-command functions
def foo(args):
    print(args.x * args.y)

def bar(args):
    print('((%s))' % args.z)

def main(args):
    print('main: %s' % args)

# create the top-level parser
parser = argparse.ArgumentParser()
parser.set_defaults(func=main)
subparsers = parser.add_subparsers()

# create the parser for the "foo" command
parser_foo = subparsers.add_parser('foo')
parser_foo.add_argument('-x', type=int, default=1)
parser_foo.add_argument('y', type=float)
parser_foo.set_defaults(func=foo)

# create the parser for the "bar" command
parser_bar = subparsers.add_parser('bar')
parser_bar.add_argument('z')
parser_bar.set_defaults(func=bar)

# parse the args and call whatever function was selected
args = parser.parse_args('foo 1 -x 2'.split())
args.func(args)


# parse the args and call whatever function was selected
args = parser.parse_args('bar XYZYX'.split())
args.func(args)

# This fails with Python 3.3.0:
args = parser.parse_args('')
args.func(args)