确切地说，什么是getattr()，我该如何使用它?

问题描述

我最近了解了getattr()函数.问题是我仍然无法理解其用法.我对getattr()唯一了解的是getattr(li, "pop")与调用li.pop相同.

I've recently read about the getattr() function. The problem is that I still can't grasp the idea of its usage. The only thing I understand about getattr() is that getattr(li, "pop") is the same as calling li.pop.

当书中提到您如何使用它来获取对函数的引用时，直到运行时才知道它的名称，我不明白.总的来说，也许这是我在编程方面的菜鸟.有人可以阐明这个话题吗?我什么时候以及如何使用它?

I didn't understand when the book mentioned how you use it to get a reference to a function without knowing its name until run-time. Maybe this is me being a noob in programming, in general. Could anyone shed some light on the subject? When and how do I use this exactly?

推荐答案

getattr(object, 'x') 与object.x完全等效.

getattr(object, 'x') is completely equivalent to object.x.

在只有两种情况中，getattr可能有用.

• 您无法编写object.x，因为您事先不知道想要哪个属性(它来自字符串).对于元编程非常有用.
• 您要提供默认值.如果没有y，则object.y将引发AttributeError.但是getattr(object, 'y', 5)将返回5.

• you can't write object.x, because you don't know in advance which attribute you want (it comes from a string). Very useful for meta-programming.
• you want to provide a default value. object.y will raise an AttributeError if there's no y. But getattr(object, 'y', 5) will return 5.

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