defaultdict 类

特点： key 不存在时会返回默认值，而不会报错

• If key exists, return its value
• If key D.N.E., return default value
  • int: returns 0
  • list: returns []
  • str: returns ""

示例

from collections import defaultdict
d = defaultdict(int)

d['apple'] = 5
print(d)
print(d['juices'])

"""
Output:
defaultdict(<class 'int'>, {'apple': 5})
0
"""