argparse_utils.py (1671B)
1 # Copyright 2015 The Chromium Authors 2 # Use of this source code is governed by a BSD-style license that can be 3 # found in the LICENSE file. 4 5 6 7 import argparse 8 9 10 class CustomHelpAction(argparse.Action): 11 '''Allows defining custom help actions. 12 13 Help actions can run even when the parser would otherwise fail on missing 14 arguments. The first help or custom help command mentioned on the command 15 line will have its help text displayed. 16 17 Usage: 18 parser = argparse.ArgumentParser(...) 19 CustomHelpAction.EnableFor(parser) 20 parser.add_argument('--foo-help', 21 action='custom_help', 22 custom_help_text='this is the help message', 23 help='What this helps with') 24 ''' 25 # Derived from argparse._HelpAction from 26 # https://github.com/python/cpython/blob/main/Lib/argparse.py 27 28 # pylint: disable=redefined-builtin 29 # (complains about 'help' being redefined) 30 def __init__(self, 31 option_strings, 32 dest=argparse.SUPPRESS, 33 default=argparse.SUPPRESS, 34 custom_help_text=None, 35 help=None): 36 super().__init__(option_strings=option_strings, 37 dest=dest, 38 default=default, 39 nargs=0, 40 help=help) 41 42 if not custom_help_text: 43 raise ValueError('custom_help_text is required') 44 self._help_text = custom_help_text 45 46 def __call__(self, parser, namespace, values, option_string=None): 47 print(self._help_text) 48 parser.exit() 49 50 @staticmethod 51 def EnableFor(parser): 52 parser.register('action', 'custom_help', CustomHelpAction)