字典经典习题

1 # 转换成字典(面试题) 这里面主要就是一个切割
2 str1 = "k:1|k1:2|k2:3|k3:4"
3 dic = {}
4 lst = str1.split("|")
5 for l in lst:
6     lst2 = l.split(":")
7     dic[lst2[0]] = lst2[1]
8 print(dic)

1 # 最直接的先初始化两个key 如果全部在一边就不太好
2 dic = {‘k1‘: [], "k2": []}
3 li = [11, 22, 33, 44, 55, 66, 77, 88, 99, 90]
4 for num in li:
5     if num > 66:
6         dic["k1"].append(num)
7     else:
8         dic["k2"].append(num)
9 print(dic)

 1 dic = {}
 2 for num in li:
 3     if num > 66:
 4         if dic.get("k1") == None:
 5             dic["k1"] = [num]
 6             # 第一次指定key1的值得时候，一定要是列表的形式
 7 
 8         else:
 9             dic["k1"].append(num)
10             # 进入列表就是append
11     else:
12         if dic.get("k2") == None:
13             dic["k2"] = [num]
14         else:
15             dic["k2"].append(num)
16 
17 print(dic)

1 dic = {}
2 for num in li:
3     if num < 66:
4         dic.setdefault(‘key1‘, []).append(num)
5     else:
6         dic.setdefault(‘key2‘, []).append(num)
7 print(dic)