利用描述符自定制property

利用描述符自定制property

class Lazyproperty:

    def __init__(self,func):

        # print('==========>',func)

        self.func=func

    def __get__(self, instance, owner):  #只有get的情况下是非数据描述符，优先级比实例的低

        print('get')

        # print(instance)

        # print(owner)

        if instance is None:   #实例调用的时候穿的是自己  类屌的时候传的是none

            return self

        res=self.func(instance)

        setattr(instance,self.func.__name__,res)#这样在非数据描述符的情况下可以实现缓存懒加载的效果，因为实例数据的优先级高于非数据描述符

        return res

    # def __set__(self, instance, value):#加上__set__后变成了数据描述符，才是数据描述符优先级只低于类，高于实例，这时候就会失去上述的懒加载效果，每次都从数据描述符中查找数据。

    #     pass

class Room:

    def __init__(self,name,width,length):

        self.name=name

        self.width=width

        self.length=length

    # @property #area=property(area)

    @Lazyproperty  #area=Lazypropery(area)

    def area(self):

        return self.width * self.length

    @property  #test=property(test)

    def area1(self):

        return  self.width * self.length

# print(Room.__dict__)

r1=Room('厕所',1,1)

# print(r1.__dict__)

#实例调用

# print(r1.area)

# print(Room.__dict__)

#类调用

# print(Room.area)

# print(r1.test)

# print(Room.test)

# print(r1.area1)

# print(r1.area1)

# print(r1.area1)

# print(r1.area1)

print(r1.area)

print(r1.__dict__)

print(r1.area)

print(r1.area)

print(r1.area)

print(r1.area)

print(r1.area)

print(r1.area)

print(r1.area)

print(r1.area)