16_描述符托管

• 一个类把属性托管给另一个类处理

class A:
    def __init__(self, val):
        self.val = val
    def __get__(self, instance, owner):
        print("调用了__get__", instance)
        return self.val
    def __set__(self, instance, value):
        print("调用了__set__", instance)
        self.val = value
    def __del__(self):
        print("调用了__del__")
        del self.val
class B:
    x = A(1000)

b = B()
b.x
b.x=12345