python真正的懶漢單例模式

 該示例不支持多線程，如果需要支持多線程，需要加鎖

class Lazy(object):
    _wrapper = {}

    def __init__(self, lazy_object, *args, **kwargs):

        self.__dict__["_wrapperobject"] = lazy_object
        self.__dict__["args"] = args
        self.__dict__["kwargs"] = kwargs

    def __getattr__(self, item, *args, **kwargs):
        if item in self.__dict__.keys():
            return self.__dict__[item]
        else:
            if self.__dict__["_wrapperobject"] not in self._wrapper.keys():
                self.init_object()
            return getattr(Lazy._wrapper[self.__dict__["_wrapperobject"]], item, *args, **kwargs)

    def __setattr__(self, key, value):
        if self.__dict__["_wrapperobject"] not in self._wrapper.keys():
            self.init_object()
        setattr(Lazy._wrapper[self.__dict__["_wrapperobject"]], key, value)

    def init_object(self):
        Lazy._wrapper[self.__dict__["_wrapperobject"]] = self._wrapperobject(*self.args, **self.kwargs)


class User:
    def __init__(self, x):
        print("10000")
        self.name = x
        self.age = 18

    def get_text(self):
        print(self.name)


class User2:
    def __init__(self, x):
        print("10000")
        self.name = x
        self.age = 18

    def get_text(self):
        print(self.age)


user = Lazy(User, "libai")
user.get_text()
user1 = Lazy(User, "lili")
user1.get_text()

user2 = Lazy(User2, "lili")
user2.get_text()