默认字典,能定义默认值为其他类型

 1 #dic1 = {}
 2 #dic1["k1"].append("kkkkk")         #正常情况会报错
 3 #print(dic1)
 4 
 5 import collections
 6 dic = collections.defaultdict(list)    #指定字典的值为列表
 7 dic["k1"].append("kkkkk")
 8 print(dic)
 9 
10 #执行结果:
11 defaultdict(<class 'list'>, {'k1': ['kkkkk']})

 

 

 1 #有如下值集合,不用默认字典执行代码如下
 2 #[11,22,33,44,55,66,77,88,99,90]
 3 #将所有大于66的值保存在字典的第一个key中,
 4 #将小于等于66的值保存在第二个key的值(列表)中。
 5 #即:{"k1":大于66,"k2":小于等于66}
 6 
 7 li = [11,22,33,44,55,66,77,88,99,90]
 8 dic = {}
 9 
10 for i in li:
11     if i>66:
12         if "k1" in dic.keys():
13             dic["k1"].append(i)
14         else:
15             dic["k1"] = [i,]
16     else:
17         if "k2" in dic.keys():
18             dic["k2"].append(i)
19         else:
20             dic["k2"] = [i,]
21 print(dic)
22 
23 #执行结果:
24 {'k2': [11, 22, 33, 44, 55, 66], 'k1': [77, 88, 99, 90]}
 1 #用默认字典精简代码
 2 from collections import defaultdict         #这样写,下面就不用写collections.defaultdict了
 3 values = [11, 22, 33,44,55,66,77,88,99,90]
 4 my_dict = defaultdict(list)     
 5 
 6 for value in  values:
 7     if value>66:
 8         my_dict['k1'].append(value)
 9     else:
10         my_dict['k2'].append(value)
11 print(my_dict)
12 
13 #执行结果:
14 defaultdict(<class 'list'>, {'k2': [11, 22, 33, 44, 55, 66], 'k1': [77, 88, 99, 90]})