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