1.__getattr__(self,name)
定義當用戶試圖獲取一個不存在的屬性時的行爲
2.__getattribute__(self,name)
定義當該類的屬性被訪問時的行爲(先於__getattr__(self,name)執行)
3.__setattr__(self,name,value)
定義當一個屬性被設置時的行爲
4.__delattr__(self,name)
定義一個屬性被刪除時的行爲
例一
class C:
def __getattribute__(self,name):
print('getattrbute')
return super().__getattribute__(name)
def __getattr__(self,name):
print('getattr')
def __setattr__(self,name,value):
print('setattr')
super().__setattr__(name,value)
def __delattr__(self,name):
print('delattr')
>>> c = C()>>> c.x=2
setattr
>>> c.s
getattrbute
getattr
例二
class Rectangle:
def __init__(self,width=0,height=0):
self.width = width
self.height = height
def __setattr__(self,name,value):
if name == 'square':
self.width = value
self.height = value
else:
super().__setattr__(name,value) #或者改爲self.__dict__[name] = value
#對象有一個特殊屬性.__dict__ 作用是以字典的形式顯示當前對象所有的屬性以及對應的值
>>> c=Rectangle()>>> c.square=10
>>> c.height
10
>>> c.width
10
>>>
>>> c.__dict__
{'width': 10, 'height': 10}