defaultdict 在 python 中接收调用对象

In [7]: from collections import defaultdict
 
In [8]: res_dict= defaultdict(int)
 
In [9]: for lang in langs:
   ...:     res_dict[lang] += 1
   ...:
 
In [10]: res_dict
Out[10]:
defaultdict(int,
            {'C#': 1,
             'java': 1,
             'kotlin': 1,
             'php': 1,
             'python': 2,
             'swift': 1})
 
In [11]: res_dict['c++']
Out[11]: 0