setattr()和object .__ setattr __()有什么区别? [英] What's the difference between setattr() and object.__setattr__()?

问题描述

我知道您不能在不是从object继承的对象上调用object.__setattr__，但是两者之间还有其他不同吗?如果这很重要，我正在使用Python 2.6.

I know that you can't call object.__setattr__ on objects not inherited from object, but is there anything else that is different between the two? I'm working in Python 2.6, if this matters.

推荐答案

再次阅读此问题，我误解了@ paper.cut在问什么:经典类和新型类之间的区别(在Python 3+中不是问题) ).我不知道答案.

Reading this question again I misunderstood what @paper.cut was asking about: the difference between classic classes and new-style classes (not an issue in Python 3+). I do not know the answer to that.

setattr(instance, name, value)是instance.__setattr__(name, value) ^** 的语法糖.

您只需要在类定义内调用object.__setattr__(...)，然后仅在直接子类化object时才调用-如果您在子类化其他内容(例如，Spam)，则应该使用super()获取层次结构中的下一个项目，或调用Spam.__setattr__(...) －这样，您就不必冒险将超类直接跳过到object来忽略超类定义的行为.

You would only need to call object.__setattr__(...) inside a class definition, and then only if directly subclassing object -- if you were subclassing something else, Spam for example, then you should either use super() to get the next item in the heirarchy, or call Spam.__setattr__(...) -- this way you don't risk missing behavior that super-classes have defined by skipping over them directly to object.

^* 适用于Python 3.0+类和2.x新型类

^* applies to Python 3.0+ classes and 2.x new-style classes

^** 在两个实例中，setattr(x, ...)和x.__setattr__(...)不同:

^**There are two instances where setattr(x, ...) and x.__setattr__(...) are not the same:

• x本身在专用字典中有一个__setattr__(所以x.__dict__[__setattr__] = ...(这几乎肯定是一个错误)

• x itself has a __setattr__ in it's private dictionary (so x.__dict__[__setattr__] = ... (this is almost certainly an error)

x.__class__具有__getattribute__方法-因为__getattribute__拦截每查找，即使该方法/属性存在

x.__class__ has a __getattribute__ method -- because __getattribute__ intercepts every lookup, even when the method/attribute exists

NB 这两个警告适用于每个语法糖快捷方式:

NB These two caveats apply to every syntactic sugar shortcut:

• setattr
• getattr
• len
• bool
• hash
• 等

• setattr
• getattr
• len
• bool
• hash
• etc

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