python身份字典 [英] python identity dictionary

问题描述

可能重复:
如何制作一个python字典，返回字典中缺少的键的键，而不是引发KeyError?

Possible Duplicate:
How to make a python dictionary that returns key for keys missing from the dictionary instead of raising KeyError?

我需要类似defaultdict的东西.但是，对于字典中没有的任何键，它都应返回键本身.

I need something like a defaultdict. However, for any key that isn't in the dictionary, it should return the key itself.

做到这一点的最佳方法是什么?

What is the best way to do that?

推荐答案

使用神奇的__missing__方法:

>>> class KeyDict(dict):
...     def __missing__(self, key):
...             return key
... 
>>> x = KeyDict()
>>> x[2]
2
>>> x[2]=0
>>> x[2]
0
>>> 

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