描述符参考的输出

Question

class C(object):  
    a = 'abc'  
    def __getattribute__(self, *args, **kwargs):  
        print("__getattribute__() is called")  
        return object.__getattribute__(self, *args, **kwargs)  
    def __getattr__(self, name):  
        print("__getattr__() is called ")  
        return name + " from getattr"  
    def __get__(self, instance, owner):  
        print("__get__() is called", instance, owner)  
        return self  
    def foo(self, x):  
        print(x)  


class C2(object):  
    d = C()  

>>>c2=C2()
>>>c2.d  
__get__() is called <__main__.C2 object at 0x000000000297BE10> <class '__main__.C2'>  
<__main__.C object at 0x000000000297BBA8>  

我明白结果，c2.d触发了C类中的get方法。

def __get__(self, instance, owner):    
    print("__get__() is called", instance, owner)    
    return self    

它打印“get() 被调用”，实例，所有者并返回自我<__main__.C object at 0x000000000297BBA8>

>>> c2.d.a  
__get__() is called <__main__.C2 object at 0x000000000297BE10> <class '__main__.C2'>  
__getattribute__() is called    
'abc'  

为什么 c2.d.a 的结果不是：

__get__() is called <__main__.C2 object at 0x000000000297BE10> <class __main__.C2'>    
<__main__.C object at 0x000000000297BBA8>      
__getattribute__() is called      
'abc'      

为什么 C 类的 get 方法中的return self 不起作用？为什么输出中在 0x000000000297BBA8> 处没有 ma​​in.C 对象？

Answer 1

ma​​in.C 对象位于 0x000000000297BBA8>

不是打印的一部分，是c2.d表达式的结果。