Function decorator

recipes/Python/578993_Keywordonly_arguments/recipe-578993.py:28–118

The decorator itself, assigns arguments as keyword-only and calculates sets for error checking. Args: wrapped: The function to decorate. Returns: A function wrapped so that it has keyword-only arguments.

(wrapped)

    """
    def decorator(wrapped):
        """The decorator itself, assigns arguments as keyword-only and
        calculates sets for error checking.

        Args:
          wrapped: The function to decorate.

        Returns:
          A function wrapped so that it has keyword-only arguments.

        """

        # Each Python 3 argument has two independent properties: it is
        # positional-and-keyword *or* keyword-only, and it has a
        # default value or it doesn't.
        names, varargs, _, defaults = inspect.getargspec(wrapped)

        # If there are no default values getargpsec() returns None
        # rather than an empty iterable for some reason.
        if defaults is None:
            defaults = ()
        names_with_defaults = frozenset(names[len(names) - len(defaults):])
        names_to_defaults = dict(zip(reversed(names), reversed(defaults)))
        if kw_only_parameters:
            kw_only_names = frozenset(kw_only_parameters)
        else:
            kw_only_names = names_with_defaults.copy()

        @functools.wraps(wrapped)
        def wrapper(*args, **kws):
            """Wrapper function, checks arguments with set operations, moves args
            from **kws into *args, and then calls wrapped().

            Args:
              *args, **kws: The arguments passed to the original function.

            Returns:
              The original function's result when it's called with the
              modified arguments.

            Raises:
              TypeError: When there is a mismatch between the supplied
                and expected arguments.

            """

            new_args = []
            args_index = 0
            for name in names:
                if name in kws:
                    # Check first if there's a bound keyword for this name
                    new_args.append(kws.pop(name))
                elif name in kw_only_names:
                    # If this name is keyword-only, check for a
                    # default or raise.
                    if name in names_to_defaults:
                        new_args.append(names_to_defaults[name])
                    else: