Try to answer this question https://twitter.com/mipsparc/status/462576919620231168

mispecparse.py

import argparse

def parse(args):
    parser = argparse.ArgumentParser()
    parser.add_argument('--send', choices=['zlib', 'bz2', 'none'], dest='send')
    parsed = parser.parse_args(args)
    if parsed.send:
        return parsed.send
    else:
        return 'zlib'

if __name__ == '__main__':
    print(parse(['--send', 'bz2']))
    print(parse([]))

i thought this solution is little shame. cooler one must be there huh.

use default keyword argument.
https://docs.python.org/dev/library/argparse.html#default