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? [英] How to make a python dictionary that returns key for keys missing from the dictionary instead of raising KeyError?

问题描述

我想创建一个 python 字典，返回字典中缺少的键的键值.

I want to create a python dictionary that returns me the key value for the keys are missing from the dictionary.

使用示例:

dic = smart_dict()
dic['a'] = 'one a'
print(dic['a'])
# >>> one a
print(dic['b'])
# >>> b

推荐答案

dicts 有一个 __missing__ 钩子:

dicts have a __missing__ hook for this:

class smart_dict(dict):
    def __missing__(self, key):
        return key

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