Python中collections.defaultdict()使用

一个小示例

from collections import  defaultdict
import json

def tree():
    return defaultdict(tree)

users = tree()
users['harold']['username'] = 'hrldcpr'
users['handler']['username'] = 'matthandlersux'

print(json.dumps(users))

输出:

{"harold": {"username": "hrldcpr"}, "handler": {"username": "matthandlersux"}}