三级菜单_要求：
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
代码实现：
首先定义好数据源
1 __author__ = "Kim Zeng"
2
3 data = {
4 '北京': {
5 "昌平": {
6 "沙河": ["冰糖葫芦", "京酱肉丝"],
7 "天通苑": ["链家地产", "我爱我家"]
8 },
9 "朝阳": {
10 "望京": ["奔驰", "奥迪"],
11 "国贸": {"百度", "HP"},
12 "东直门": {"大街", "小米"},
13 },
14 "海淀": {"敏", "烤鸭"},
15 },
16 '山东': {
17 "德州": {"扒鸡"},
18 "青岛": {"啤酒"},
19 "济南": {"红枣"}
20 },
21 '广东': {
22 "东莞": {"美女"},
23 "深圳": {"汽车"},
24 "佛山": {"照明"},
25 }
26 }
实现功能：
1 exit_flag = False #设置一个标识位
2 while not exit_flag:
3 for i in data:
4 print(i)
5 choose = input("第一层>>>")
6 if choose == 'b':
7 print("不能再返回了>>>")
8 continue
9 elif choose == 'q':
10 exit_flag = True
11 elif choose not in data:
12 print("不存在，重新输入>>>")
13 continue
14 else:
15 while not exit_flag:
16 for i2 in data[choose]:
17 print("\t", i2)
18 choose2 = input("第二层>>>")
19 if choose2 == 'b':
20 break
21 elif choose2 == 'q':
22 exit_flag = True
23 elif choose2 not in data[choose]:
24 print("不存在，重新输入>>>")
25 continue
26 else:
27 while not exit_flag:
28 for i3 in data[choose][choose2]:
29 print("\t\t", i3)
30 choose3 = input("第三层>>>")
31 if choose3 == 'b':
32 break
33 elif choose3 == 'q':
34 exit_flag = True
35 elif choose3 not in data[choose][choose2]:
36 print("不存在，重新输入>>>")
37 continue
38 else:
39 while not exit_flag:
40 choose4 = input("最后了，b返回，q退出>>>")
41 if choose4 == 'b':
42 break
43 elif choose4 == 'q':
44 exit_flag = True
45 for i4 in data[choose][choose2]:
46 print("\t\t", i4)
标签：菜单,示例,flag,exit,choose,print,data,三级 From： https://www.cnblogs.com/zcest/p/17222626.html