def set_default_subparser(self, name, args=None):
    """see http://stackoverflow.com/questions/5176691/argparse-how-to-specify-a-default-subcommand"""
    subparser_found = False
    for arg in sys.argv[1:]:
        if arg in ['-h', '--help', '--version']:  # global help/version if no subparser
            break
    else:
        for x in self._subparsers._actions:
            if not isinstance(x, argparse._SubParsersAction):
                continue
            for sp_name in x._name_parser_map.keys():
                if sp_name in sys.argv[1:]:
                    subparser_found = True
        if not subparser_found:
            # insert default in first position, this implies no
            # global options without a sub_parsers specified
            if args is None:
                sys.argv.insert(1, name)
            else:
                args.insert(0, name)
see http://stackoverflow.com/questions/5176691/argparse-how-to-specify-a-default-subcommand
electrum/commands.py