def create_parser():
    root_parser = ArgumentParser(description='article fetch operations')
    root_parser.add_argument('--list_home', help='list lookup directory')
    add_subparsers(root_parser.add_subparsers())
    return root_parser


def add_subparsers(subparsers):
    parser_list = subparsers.add_parser('list')
    parser_list.add_argument('target_list', nargs='?',
                             help='Name of the list or list file')
    parser_list.set_defaults(func=get_list)
    ...
    
def main(argv=None):
    parser = create_parser()
    args = parser.parse_args(argv)
    kwargs = dict(args._get_kwargs())
    args.func(**kwargs)
    return
    
if __name__ == '__main__':
    sys.exit(main())