编写三级菜单：
1. 运行程序输出第一级菜单
2. 选择一级菜单某项，输出二级菜单，同理输出三级菜单
3. 菜单数据保存在文件中
4. 让用户选择是否要退出
5. 有返回上一级菜单的功能
1 # Author: zfh
2
3 data = {
4 "陕西":{
5 "汉中":["张骞故里","古汉台"],
6 "西安":[],
7 "商洛":[]
8 },
9 "山西":{
10 "太远":[],
11 "运城":[],
12 "平凉":[]
13 },
14 "山东":{
15 "青岛":[],
16 "济南":[],
17 "聊城":[]
18 }
19 }
20 exit_flag = False
21 while not exit_flag:
22 for i in data:
23 print(i)
24 choice = input("请输入选择1>>:")
25 if choice in data:
26 while not exit_flag:
27 for i1 in data[choice]:
28 print(" ",i1)
29 choice1 = input("请输入选择2>>:")
30 if choice1 in data[choice]:
31 while not exit_flag:
32 for i2 in data[choice][choice1]:
33 print(" ",i2)
34 choice2 = input("最后一层，按b返回>>:")
35 if choice2 == "b":
36 pass
37 elif choice2 == "q":
38 exit_flag = True
39 if choice1 == "b":
40 break
41 elif choice1 == "q":
42 exit_flag = True
43 if choice == "b":
44 break
45 elif choice =="q":
46 exit_flag = True