如何在Python 3中实现UserDict.DictMixin的功能？

问题描述

在Python 3中， UserDict.DictMixin 类被移动到集合模块。该文档建议在其位置使用 collections.MutableMapping ，但是这个抽象类不提供许多方法， DictMixin do / did。

In Python 3 the UserDict.DictMixin class was moved to the collections module. The docs suggest using collections.MutableMapping in its place, however this abstract class does not provide a number of the methods that the DictMixin does/did.

是否有另一种（或更好）的方式来定义它们，而不是抓取 UserDict.Mixin的私人副本来源（或者只是将需要的部分）复制到我自己的字典类中？

Is there another (or better) way to define them short of grabbing a private copy of the UserDict.Mixin source for importing (or perhaps just copying the needed portions of) it into my own dictionary-like class?

推荐答案

方法的数量特别是 __ len __ 和 __ iter __ ，所以额外的工作不是那么多。

The "number of methods" are specifically __len__ and __iter__ so the additional work is not that much.

def __len__(self):
    return len(self.mylist)

def __iter__(self):
    for i in self.mylist:
        yield i

应该工作，我想（未经测试，但是）。

Should work, I think (untested, though).

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