类和对象-描述符

BrightXiong

>>> #描述符（property的原理）：P177  实现了__get__()/__set__()/__delete__()三个中任何一个或多个方法的类，称为描述符
>>> class D:
    def __get__(self, instance, owner):
        print(f'get~\nself -> {self}\ninstance -> {instance}\nowner -> {owner}')
    def __set__(self, instance, value):
        print(f'set~\nself -> {self}\ninstance -> {instance}\nvalue -> {value}')
    def __delete__(self, instance):# 不要混淆__del__()
        print(f'delete~\nself -> {self}\ninstance -> {instance}')
...
>>> # 类D 为描述符，在另一个类里将他的实例化对象赋值给想要管理的属性就能启用他
>>> class C:
...         x = D()
...
>>> c = C()

>>> c.x = 250
set~
self -> <__main__.D object at 0x00FBE1D8>
instance -> <__main__.C object at 0x00FBE208>
value -> 250

>>> c.x
get~
self -> <__main__.D object at 0x00FBE1D8>
instance -> <__main__.C object at 0x00FBE208>
owner -> <class '__main__.C'>

>>> del c.x
delete~
self -> <__main__.D object at 0x00FBE1D8>
instance -> <__main__.C object at 0x00FBE208>
>>>
# self参数对应的是描述符这个类的实例对象<__main__.D object at 0x0000026F6A728FA0>
# instance对应的是被描述符拦截的属性所在的类的实例对象<__main__.C object at 0x0000026F6A728F70>
# owner参数对应被描述符拦截的属性所在的类<class '__main__.C'>
>>>