Python Language
正確なヘルプ出力を持つCLIサブコマンド

前書き

備考

usage: sub <command>

commands:

  status -  show status
  list   -  print list

ネイティブ・ウェイ（ライブラリなし）

"""
usage: sub <command>

commands:

  status -  show status
  list   -  print list
"""

import sys

def check():
    print("status")
    return 0

if sys.argv[1:] == ['status']:
    sys.exit(check())
elif sys.argv[1:] == ['list']:
    print("list")
else:
    print(__doc__.strip())

引数のない出力：

usage: sub <command>

commands:

  status -  show status
  list   -  print list

長所：

• デセップなし
• 誰もがそれを読むことができるはずです
• ヘルプの書式設定を完全に制御

argparse（デフォルトヘルプフォーマッタ）

import argparse
import sys

def check():
    print("status")
    return 0

parser = argparse.ArgumentParser(prog="sub", add_help=False)
subparser = parser.add_subparsers(dest="cmd")

subparser.add_parser('status', help='show status')
subparser.add_parser('list', help='print list')

# hack to show help when no arguments supplied
if len(sys.argv) == 1:
    parser.print_help()
    sys.exit(0)

args = parser.parse_args()

if args.cmd == 'list':
    print('list')
elif args.cmd == 'status':
    sys.exit(check())

引数のない出力：

usage: sub {status,list} ...

positional arguments:
  {status,list}
    status       show status
    list         print list

長所：

• Pythonに付属
• オプションの解析が含まれています

argparse（カスタムヘルプフォーマッタ）

修正されたヘルプ出力のhttp://www.riptutorial.com/python/example/25282/argparse--default-help-formatterの拡張版です。

import argparse
import sys

class CustomHelpFormatter(argparse.HelpFormatter):
    def _format_action(self, action):
        if type(action) == argparse._SubParsersAction:
            # inject new class variable for subcommand formatting
            subactions = action._get_subactions()
            invocations = [self._format_action_invocation(a) for a in subactions]
            self._subcommand_max_length = max(len(i) for i in invocations)

        if type(action) == argparse._SubParsersAction._ChoicesPseudoAction:
            # format subcommand help line
            subcommand = self._format_action_invocation(action) # type: str
            width = self._subcommand_max_length
            help_text = ""
            if action.help:
                help_text = self._expand_help(action)
            return "  {:{width}} -  {}\n".format(subcommand, help_text, width=width)

        elif type(action) == argparse._SubParsersAction:
            # process subcommand help section
            msg = '\n'
            for subaction in action._get_subactions():
                msg += self._format_action(subaction)
            return msg
        else:
            return super(CustomHelpFormatter, self)._format_action(action)


def check():
    print("status")
    return 0

parser = argparse.ArgumentParser(usage="sub <command>", add_help=False,
             formatter_class=CustomHelpFormatter)

subparser = parser.add_subparsers(dest="cmd")
subparser.add_parser('status', help='show status')
subparser.add_parser('list', help='print list')

# custom help messge
parser._positionals.title = "commands"

# hack to show help when no arguments supplied
if len(sys.argv) == 1:
    parser.print_help()
    sys.exit(0)

args = parser.parse_args()

if args.cmd == 'list':
    print('list')
elif args.cmd == 'status':
    sys.exit(check())

引数のない出力：

usage: sub <command>

commands:

  status -  show status
  list   -  print list