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 = False21 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("\t",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("\t\t",i2)34                     choice2 = input("最后一层，按b返回>>:")35                     if choice2 == "b":36                         pass37                     elif choice2 == "q":38                         exit_flag = True39             if choice1 == "b":40                 break41             elif choice1 == "q":42                 exit_flag = True43     if choice == "b":44         break45     elif choice =="q":46         exit_flag = True