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如何在 python 中覆盖类属性访问?

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2022-01-01

How can I override class attribute access in python?(如何在 python 中覆盖类属性访问?)

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问题描述

如何在 python 中覆盖类属性访问?

How can I override class attribute access in python?

附:有没有办法单独保留对类属性的常规访问，但在缺少属性时调用更具体的异常?

P.S. Is there a way to leave regular access to class attributes alone but calling a more specific exception on missing attribute?

推荐答案

__getattr__ 属性在实例/类/父类上不存在时调用魔术方法.您可以使用它为缺少的属性引发特殊异常:

The __getattr__ magic method is called when the attribute doesn't exist on the instance / class / parent classes. You'd use it to raise a special exception for a missing attribute:

class Foo(object):
    def __getattr__(self, attr):
        # only called when self.attr doesn't exist
        raise MyCustonException(attr)

如果要自定义访问类属性，需要在元类/类型上定义__getattr__:

If you want to customize access to class attributes, you need to define __getattr__ on the metaclass / type:

class BooType(type):
    def __getattr__(self, attr):
        print attr
        return attr

class Boo(object):
    __metaclass__ = BooType

boo = Boo()
Boo.asd # prints asd
boo.asd # raises an AttributeError like normal

如果您想自定义 all 属性访问，请使用 __getattribute__ 魔术方法.

If you want to customize all attribute access, use the __getattribute__ magic method.

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