options.py 文件源码

def define(self, name, default=None, type=None, help=None, metavar=None,
               multiple=False, group=None, callback=None):
        """Defines a new command line option.

        If ``type`` is given (one of str, float, int, datetime, or timedelta)
        or can be inferred from the ``default``, we parse the command line
        arguments based on the given type. If ``multiple`` is True, we accept
        comma-separated values, and the option value is always a list.

        For multi-value integers, we also accept the syntax ``x:y``, which
        turns into ``range(x, y)`` - very useful for long integer ranges.

        ``help`` and ``metavar`` are used to construct the
        automatically generated command line help string. The help
        message is formatted like::

           --name=METAVAR      help string

        ``group`` is used to group the defined options in logical
        groups. By default, command line options are grouped by the
        file in which they are defined.

        Command line option names must be unique globally. They can be parsed
        from the command line with `parse_command_line` or parsed from a
        config file with `parse_config_file`.

        If a ``callback`` is given, it will be run with the new value whenever
        the option is changed.  This can be used to combine command-line
        and file-based options::

            define("config", type=str, help="path to config file",
                   callback=lambda path: parse_config_file(path, final=False))

        With this definition, options in the file specified by ``--config`` will
        override options set earlier on the command line, but can be overridden
        by later flags.
        """
        if name in self._options:
            raise Error("Option %r already defined in %s" %
                        (name, self._options[name].file_name))
        frame = sys._getframe(0)
        options_file = frame.f_code.co_filename
        file_name = frame.f_back.f_code.co_filename
        if file_name == options_file:
            file_name = ""
        if type is None:
            if not multiple and default is not None:
                type = default.__class__
            else:
                type = str
        if group:
            group_name = group
        else:
            group_name = file_name
        self._options[name] = _Option(name, file_name=file_name,
                                      default=default, type=type, help=help,
                                      metavar=metavar, multiple=multiple,
                                      group_name=group_name,
                                      callback=callback)