Python argparse require选项，取决于定义的标志

您可以使用y / be作为子命令定义子解析器，或者为a声明第二个解析器实例。就像是：

parser = argparse.ArgumentParser(
    description="An example",
    formatter_class=argparse.RawTextHelpFormatter
)
# ensure either option -a or -b only
group = parser.add_mutually_exclusive_group(required=True)
group.add_argument("-a", "--ay", help="Method A, requires file.",
                   action='store_true')
group.add_argument("-b", "--be", help="Method B, no file required.",
                   action='store_true')
# define a parser for option -a
parser_a = argparse.ArgumentParser()
parser_a.add_argument("-f", "--file", help="A file, used with method A.",
                      type=check_file, required=True)
parser_a.add_argument("-a", "--ay", help="Method A, requires file.",
                      action='store_true')

# first parse - get either -a/-b
args = parser.parse_known_args(sys.argv[1:])
# if -a, use the second parser to ensure -f is in argument
# note parse_known_args return tuple, the first one is the populated namespace
if args[0].ay:
    args = parser_a.parse_args(sys.argv[1:])