# coding: utf-8


class A(object):
    a = "A.class"

    def __init__(self):
        self.a = "A.instance"
        pass

    def __getattribute__(self, item):
        return "A.__getattribute__"

    def __getattr__(self, item):
        return "A.__getattr__"


class B(A):
    a = "B.class"

    def __init__(self):
        super(B, self).__init__()
        self.a = "B.instance"
        pass

    def __getattribute__(self, item):
        return "B.__getattribute__"

    def __getattr__(self, item):
        return "B.__getattr__"

inst = B()

print inst.a

子类父类所有获取属性的方法都在时，最先调用的是当前类的__getattribute__方法，依次注释当前调用到的方法，查看下一个调用的方法是什么，出现的顺序如下所示：

• B.__getattribute__
• A.__getattribute__
• B.instance
• A.instance
• B.class
• A.class
• B.__getattr__
• A.__getattr__
• AttributeError: 'B' object has no attribute 'a'