Argparse和ArgumentDefaultsHelpFormatter.选择sys.stdin/stdout作为默认值时格式化默认值

您可以将ArgumentDefaultsHelpFormatter子类化以执行所需的操作。

from argparse import ArgumentDefaultsHelpFormatter,RawDescriptionHelpFormatter

class CustomFormatter(argparse.ArgumentDefaultsHelpFormatter, argparse.RawDescriptionHelpFormatter):
    def _get_help_string(self, action):
        help = action.help
        if '%(default)' not in action.help:
            if action.default is not argparse.SUPPRESS:
                defaulting_nargs = [argparse.OPTIONAL, argparse.ZERO_OR_MORE]
                if action.option_strings or action.nargs in defaulting_nargs:
                    if type(action.default) == type(sys.stdin):
                        print action.default.name
                        help += ' (default: ' + str(action.default.name) + ')'
                    else:
                        help += ' (default: %(default)s)'
        return help

parser = argparse.ArgumentParser(prog='PROG', formatter_class=CustomFormatter)

optional arguments:
  -h, --help            show this help message and exit
  --infile File, -i File
                        The input file/stream. (default: )
  --outfile File, -o File
                        The output file/stream. (default: )
  --whatever-arg WHATEVER_ARG, -w WHATEVER_ARG
                        Change something (default: any)