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>

我理解结果，c2.d触发C类中的 get 方法。

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

打印“获取（）被称为”，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 get 方法中的return self不起作用？为什么在0x000000000297BBA8＆gt;处没有＆lt; main .C对象在输出？

Answer 1

＆lt; main .C对象位于0x000000000297BBA8＆gt;

不是打印的一部分，它是c2.d表达式的结果。

描述符引用的输出

1 个答案: