高级super实例

  1 class CommandParser(ArgumentParser):
  2     """
  3     Customized ArgumentParser class to improve some error messages and prevent
  4     SystemExit in several occasions, as SystemExit is unacceptable when a
  5     command is called programmatically.
  6     """
  7     def __init__(self, cmd, **kwargs):
  8         self.cmd = cmd
  9         super(CommandParser, self).__init__(**kwargs)
 10 
 11     def parse_args(self, args=None, namespace=None):
 12         # Catch missing argument for a better error message
 13         if (hasattr(self.cmd, ‘missing_args_message‘) and
 14                 not (args or any(not arg.startswith(‘-‘) for arg in args))):
 15             self.error(self.cmd.missing_args_message)
 16         return super(CommandParser, self).parse_args(args, namespace)
 17 
 18 class ArgumentParser(_AttributeHolder, _ActionsContainer):
 19     """Object for parsing command line strings into Python objects.
 20 
 21     Keyword Arguments:
 22         - prog -- The name of the program (default: sys.argv[0])
 23         - usage -- A usage message (default: auto-generated from arguments)
 24         - description -- A description of what the program does
 25         - epilog -- Text following the argument descriptions
 26         - parents -- Parsers whose arguments should be copied into this one
 27         - formatter_class -- HelpFormatter class for printing help messages
 28         - prefix_chars -- Characters that prefix optional arguments
 29         - fromfile_prefix_chars -- Characters that prefix files containing
 30             additional arguments
 31         - argument_default -- The default value for all arguments
 32         - conflict_handler -- String indicating how to handle conflicts
 33         - add_help -- Add a -h/-help option
 34         - allow_abbrev -- Allow long options to be abbreviated unambiguously
 35     """
 36 
 37     def __init__(self,
 38                  prog=None,
 39                  usage=None,
 40                  description=None,
 41                  epilog=None,
 42                  parents=[],
 43                  formatter_class=HelpFormatter,
 44                  prefix_chars=‘-‘,
 45                  fromfile_prefix_chars=None,
 46                  argument_default=None,
 47                  conflict_handler=‘error‘,
 48                  add_help=True,
 49                  allow_abbrev=True):
 50 
 51         superinit = super(ArgumentParser, self).__init__
 52         superinit(description=description,
 53                   prefix_chars=prefix_chars,
 54                   argument_default=argument_default,
 55                   conflict_handler=conflict_handler)
 56 
 57 
 58         # default setting for prog
 59         if prog is None:
 60             prog = _os.path.basename(_sys.argv[0])
 61 
 62         self.prog = prog
 63         self.usage = usage
 64         self.epilog = epilog
 65         self.formatter_class = formatter_class
 66         self.fromfile_prefix_chars = fromfile_prefix_chars
 67         self.add_help = add_help
 68         self.allow_abbrev = allow_abbrev
 69 
 70         add_group = self.add_argument_group
 71         self._positionals = add_group(_(‘positional arguments‘))
 72         self._optionals = add_group(_(‘optional arguments‘))
 73         self._subparsers = None
 74 
 75         # register types
 76         def identity(string):
 77             return string
 78         self.register(‘type‘, None, identity)
 79 
 80         # add help argument if necessary
 81         # (using explicit default to override global argument_default) 显式覆盖全局
 82         default_prefix = ‘-‘ if ‘-‘ in prefix_chars else prefix_chars[0]
 83         if self.add_help:
 84             self.add_argument(
 85                 default_prefix+‘h‘, default_prefix*2+‘help‘,
 86                 action=‘help‘, default=SUPPRESS,
 87                 help=_(‘show this help message and exit‘))
 88 
 89         # add parent arguments and defaults
 90         for parent in parents:
 91             self._add_container_actions(parent)
 92             try:
 93                 defaults = parent._defaults
 94             except AttributeError:
 95                 pass
 96             else:
 97                 self._defaults.update(defaults)
 98 
 99         def parse_args(self, args=None, namespace=None):
100         args, argv = self.parse_known_args(args, namespace)
101         if argv:
102             msg = _(‘unrecognized arguments: %s‘)
103             self.error(msg % ‘ ‘.join(argv))
104         return args