物件導向-描述符

標籤：ini   val   注釋   instance   ===   描述   UNC   delete   屬性   

描述符使用

Foo接管了Bar的x值，當x值被操作的時候都調用Foo相應的get/set/delete操作

class Foo:    def __get__(self,instance,owner):        print(‘===>get‘,instance,owner)    def __set__(self,instance,value):        print(‘===>set‘,instance,value)    def __delete__(self, instance):        print(‘===>delete‘,instance)class Bar:    x = Foo()    def __init__(self,n):        self.x = nb1 = Bar(10)print(b1.__dict__)print(Bar.__dict__)print(b1.x)‘‘‘===>set <__main__.Bar object at 0x0000022A4A214D68> 10{}{‘__module__‘: ‘__main__‘, ‘x‘: <__main__.Foo object at 0x0000022A4A214C50>, ‘__init__‘: <function Bar.__init__ at 0x0000022A4A1F6C80>, ‘__dict__‘: <attribute ‘__dict__‘ of ‘Bar‘ objects>, ‘__weakref__‘: <attribute ‘__weakref__‘ of ‘Bar‘ objects>, ‘__doc__‘: None}===>get <__main__.Bar object at 0x0000022A4A214D68> <class ‘__main__.Bar‘>None‘‘‘

class Foo:    def __get__(self,instance,owner):        print(‘===>get‘,instance,owner)    def __set__(self,instance,value):        print(‘===>set‘,instance,value)    def __delete__(self, instance):        print(‘===>delete‘,instance)class Bar:    x = Foo()    def __init__(self,n):        self.x = n# print(Bar.x)# Bar.x = 1 #不觸發描述符，因為類屬性優先順序更高,如果不注釋，後面的語句也不觸發描述符b1 = Bar(10)print(b1.x)del b1.x‘‘‘===>set <__main__.Bar object at 0x000001D368C14CF8> 10===>get <__main__.Bar object at 0x000001D368C14CF8> <class ‘__main__.Bar‘>None===>delete <__main__.Bar object at 0x000001D368C14CF8>‘‘‘

描述符優先順序

1. 類屬性
2. 資料描述符
3. 執行個體屬性
4. 非資料描述符
5. 找不到的屬性觸發__getattr__()

class Foo:    def __get__(self,instance,owner):        print(‘===>get‘,instance,owner)    def __set__(self,instance,value):        print(‘===>set‘,instance,value)    def __delete__(self, instance):        print(‘===>delete‘,instance)class Bar:    x = Foo()    def __init__(self,n):        self.x = n# print(Bar.x)Bar.x = 1 #不觸發描述符，因為類屬性優先順序更高‘‘‘Process finished with exit code 0‘‘‘

物件導向-描述符