Python备忘录模式

备忘录模式，类似于撤销功能，提供保存并恢复之前状态的功能。

class Momento(object):
    def __init__(self):
        super().__init__()
        self.dct = {}

    def set_status(self, dct):
        self.dct = {}
        for key in dct:
            if not key.startswith('_'):
                self.dct[key] = dct[key]

    def get_status(self):
        return self.dct


class Obj(object):
    def __init__(self, a):
        super().__init__()
        self.attribute_a = a

        self._momento = Momento()

    def set_a(self, status):
        self.backup_current_status()
        self.attribute_a = status

    def restore_previous_status(self):
        self.__dict__.update(self._momento.get_status())

    def backup_current_status(self):
        self._momento.set_status(self.__dict__)

    def __str__(self):
        return "attribute_a: " + self.attribute_a + '\n'


def main():
    obj = Obj('a')
    obj.set_a('aa')
    print('current_status:\n', obj)
    obj.restore_previous_status()
    print('previous_status:\n', obj)


if __name__ == '__main__':
    main()