1. __getattr__(self, item):

在訪問對(duì)象的item屬性的時(shí)候，如果對(duì)象并沒有這個(gè)相應(yīng)的屬性，方法，那么將會(huì)調(diào)用這個(gè)方法來處理。。。這里要注意的時(shí)，假如一個(gè)對(duì)象叫fjs, ?他有一個(gè)屬性：fjs.name = "fjs"，那么在訪問fjs.name的時(shí)候因?yàn)楫?dāng)前對(duì)象有這個(gè)屬性，那么將不會(huì)調(diào)用__getattr__()方法，而是直接返回了擁有的name屬性了

2. __setattr__(self, item, value):

當(dāng)試圖對(duì)象的item特性賦值的時(shí)候?qū)?huì)被調(diào)用。

# -*- coding:utf-8 -*- class Student:def __init__(self, work, score):self.work = workself.score = scoredef __getattr__(self, item):return item + ' is not exits'def __setattr__(self, key, value):self.__dict__[key] = value#object.__setattr__(self, key, value) 兩條語句等效def __delattr__(self, name):print("你正在刪除一個(gè)屬性")return super().__delattr__(name)def __getitem__(self, item):return self.__dict__[item]def __setitem__(self, key, value):self.__dict__[key] = values = Student() print(s.name) # 調(diào)用__getattr__方法 輸出'name is not exits' s.age = 1 # 調(diào)用__setattr__ 方法 print(s.age) # 輸出 1 print(s['age']) # 調(diào)用 __getitem__方法 輸出1 s['name'] = 'tom' # 調(diào)用 __setitem__ 方法 print(s['name']) # 調(diào)用 __getitem__ 方法 輸出 'tom'del s.work # 調(diào)用__delattr__方法 try:print(s.work) # 輸出 'MyClass' object has no attribute 'work' except AttributeError as reason:print(reason)

輸出結(jié)果為：

name is not exits 1 1 tom

3.?__getattribute__

class C(object):a = 'abc'def __getattribute__(self, *args, **kwargs):print("__getattribute__() is called")return object.__getattribute__(self, *args, **kwargs) # return "haha"def __getattr__(self, name):print("__getattr__() is called ")return name + " from getattr"def __get__(self, instance, owner):print("__get__() is called", instance, owner)return selfdef foo(self, x):print(x)class C2(object):d = C() if __name__ == '__main__':c = C()c2 = C2()print(c.a)print(c.zzzzzzzz)c2.dprint(c2.d.a)

?輸出結(jié)果

__getattribute__() is called abc __getattribute__() is called __getattr__() is called zzzzzzzz from getattr __get__() is called <__main__.C2 object at 0x16d2310> <class '__main__.C2'> __get__() is called <__main__.C2 object at 0x16d2310> <class '__main__.C2'> __getattribute__() is called abc

?

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