如何编写静态python getitem方法? [英] How to write a static python getitem method?

问题描述

要进行这项工作，我需要更改什么?

What do I need to change to make this work?

class A:
    @staticmethod
    def __getitem__(val):
        return "It works"

print A[0]

请注意，我正在以A类型调用__getitem__方法.

Note that I am calling the __getitem__ method on the type A.

推荐答案

为对象建立索引时，将首先在对象的类中查找特殊方法__getitem__.一个类本身就是一个对象，一个类的类通常是type.因此，要为类覆盖__getitem__，您可以重新定义其元类(使其成为type的子类):

When an object is indexed, the special method __getitem__ is looked for first in the object's class. A class itself is an object, and the class of a class is usually type. So to override __getitem__ for a class, you can redefine its metaclass (to make it a subclass of type):

class MetaA(type):
    def __getitem__(cls,val):
        return "It works"

class A(object):
    __metaclass__=MetaA
    pass

print(A[0])
# It works

---

在Python3中，元类是通过以下方式指定的:

---

In Python3 the metaclass is specified this way:

class A(object, metaclass=MetaA):
    pass

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