python 字典中的value 不在字典中,key才在

#字典中的value 不在字典中
> my_dictionary = {1: 'one', 2: 'two', 3: 'three'}
> 1 in my_dictionary
True
> 'one' in my_dictionary
False

 

python默认字典手册defaultdict()

https://docs.python.org/3.3/library/collections.html#collections.defaultdict