为什么覆盖__getattribute__代理一个价值螺丝起来isinstance？ [英] Why does overriding __getattribute__ to proxy a value screw up isinstance?

问题描述

为什么会发生这种情况？

Why does this happen?

class IsInstanceScrewer(object):
    def __init__(self, value):
        self.value = value

    def __getattribute__(self, name):
        if name in ('value',):
            return object.__getattribute__(self, name)
        value = object.__getattribute__(self, 'value')
        return object.__getattribute__(value, name)

isinstance(IsInstanceScrewer(False), bool) #True
isinstance(IsInstanceScrewer([1, 2, 3]), list) #True

推荐答案

__ getattribute__这个类绝对不是bool的实例正在返回包装值的 __ class __ ，而不是自己的 __ class __ ：

__getattribute__ is returning the __class__ of the wrapped value instead of its own __class__:

>>> class IsInstanceScrewer(object):
    def __init__(self, value):
        self.value = value

    def __getattribute__(self, name):
        print name
        if name in ('value',):
            return object.__getattribute__(self, name)
        value = object.__getattribute__(self, 'value')
        return object.__getattribute__(value, name)

>>> isinstance(IsInstanceScrewer(False), bool)
__class__
True
>>> isinstance(IsInstanceScrewer([1, 2, 3]), list)
__class__
True

$ b b

这可能是所期望的行为，或者不取决于你在做什么。

This may be desired behavior or not depending on what you're doing.

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