__init__と__repr__を書く労力を低減するための混ぜ込みクラス

mixin.py

class once:
    def __init__(self, f):
        self.f = f
        self.memo = {}

    def __call__(self, *args):
        if args in self.memo:
            return self.memo[args]
        else:
            result = self.f(*args)
            self.memo[args] = result
            return result

@once
def MultiMix(*params):
    """Example usage:
    >>> class Hoge(MultiMix('x', 'y', 'z')):
    ...    def sum(self):
    ...        return self.x + self.y + self.z
    ...    def product(self):
    ...        return self.x * self.y * self.z
    >>> hoge = Hoge(1, 2, 4)
    >>> hoge
    Hoge(1, 2, 4)
    >>> hoge.sum()
    7
    >>> hoge.product()
    8
    """
    def __init__(self, *args, **kwargs):
        arg = iter(args)
        for name in params:
            try:
                value = next(arg)
            except StopIteration:
                value = kwargs[name]
            self.__dict__[name] = value
        
    def __repr__(self):
        return self.__class__.__name__ + "(" + ", ".join(I.imap(repr, I.imap(self.__dict__.__getitem__, params))) + ")"
    return type("MultiMix({!r})".format(params), (object,), {"__init__": __init__, "__repr__": __repr__})