一、代码需求：
编写一个三级菜单：
1、可依次进入各菜单；
2、输入 “back” 可返回上一级菜单；
3、每一级菜单输入 “quit” 可退出程序。
二、程序代码：
第一版代码：
1 #！/user/bin/env ptyhon 2 # -*- coding:utf-8 -*- 3 # Author: VisonWong 4 5 province = ['河南', '陕西'] 6 city = ['郑州', '洛阳', '三门峡', '西安', '渭南', '宝鸡'] 7 city_henan = ['郑州', '洛阳', '三门峡'] 8 city_shanxi = ['西安', '渭南', '宝鸡'] 9 country_zhengzhou = ['金水区', '二七区', '惠济区', '中原区', '上街区'] 10 country_luoyang = ['涧西区', '西工区', '老城区', '洛龙区', '吉利区'] 11 country_sanmenxia = ['灵宝市', '卢氏', '义马市', '陕县'] 12 country_xian = ['碑林区', '莲湖区', '雁塔区', '未央区', '灞桥区'] 13 country_weinan = ['临渭区', '华阴市', '韩城', '华县', '潼关'] 14 country_baoji = ['金台区', '渭滨区', '岐山县'] 15 16 province_city = { 17 '河南' : city_henan, 18 '陕西' : city_shanxi 19 } 20 city_country = { 21 '郑州' : country_zhengzhou, 22 '洛阳' : country_luoyang, 23 '三门峡': country_sanmenxia, 24 '西安' : country_xian, 25 '渭南' : country_weinan, 26 '宝鸡' : country_baoji 27 } 28 T = True 29 T1 = True 30 while T: 31 print(province) 32 flag = True 33 province_input = input('Please choose one province to find out or input exit to quit!') 34 if province_input == 'exit': 35 break 36 else: 37 for i in province: 38 if province_input == i: 39 print(province_city[i]) 40 i1=i 41 flag = False 42 if flag: 43 print('Cheak your input') 44 continue 45 while T1: 46 city_input = input('Please choose one city to find out ' 47 'or input back to last menu or input exit to quit!') 48 if city_input == 'exit': 49 T = False 50 T1 = False 51 elif city_input == 'back': 52 break 53 else: 54 for j in city: 55 if city_input == j: 56 print(city_country[j]) 57 country_input = input('Please input back to last menu or input exit to quit!') 58 if country_input == 'exit': 59 T = False 60 T1 = False 61 elif country_input == 'back': 62 print(province_city[i1]) 63 break 64 print ('Have Fun !')
第二版代码：
1 #！/user/bin/env ptyhon 2 # -*- coding:utf-8 -*- 3 # Author: VisonWong 4 5 #定义三级菜单 6 menu = { 7 '河南': { 8 '郑州': ['金水区', '二七区', '惠济区', '中原区', '上街区'], 9 '洛阳': ['涧西区', '西工区', '老城区', '洛龙区', '吉利区'], 10 '三门峡' : ['灵宝市', '卢氏', '义马市', '陕县'] 11 }, 12 '陕西': { 13 '西安': ['碑林区', '莲湖区', '雁塔区', '未央区', '灞桥区'], 14 '渭南': ['临渭区', '华阴市', '韩城', '华县', '潼关'], 15 '宝鸡': ['涧西区', '西工区', '老城区', '洛龙区', '吉利区'] 16 } 17 } 18 19 continue_flag = True 20 21 while continue_flag: 22 for i in menu: 23 print(i) 24 province_input = input('Please choose one province to find out or input exit to quit!') 25 if province_input in menu: 26 #因为每级菜单都需要反复进入，故引入循环嵌套 27 while continue_flag: 28 for i1 in menu[province_input]: 29 print(i1) 30 city_input = input('Please choose one city to find out 31 or input back to last menu or input exit to quit!') 32 if city_input in menu[province_input]: 33 34 while continue_flag: 35 for i2 in menu[province_input][city_input]: 36 print(i2) 37 country_input = input('Please input back to last menu or input exit to quit!') 38 if country_input == 'back': 39 break 40 elif country_input == 'quit': 41 continue_flag = False 42 else: 43 print("Please check your input!") 44 45 elif city_input == 'back': 46 break 47 elif city_input == 'quit': 48 continue_flag = False 49 else: 50 print("Please check your input!") 51 52 elif province_input == 'quit': 53 continue_flag = False 54 else: 55 print("Please check your input!")
输出结果：
1 E:PythonPythonExercisingMenuvenvScriptspython.exe E:/Python/PythonExercising/Menu/3level_menu.py 2 河南 3 陕西 4 Please choose one province to find out or input exit to quit!上海 5 Please check your input! 6 河南 7 陕西 8 Please choose one province to find out or input exit to quit!河南 9 郑州 10 洛阳 11 三门峡 12 Please choose one city to find out or input back to last menu or input exit to quit!三门峡 13 灵宝市 14 卢氏 15 义马市 16 陕县 17 Please input back to last menu or input exit to quit!back 18 郑州 19 洛阳 20 三门峡 21 Please choose one city to find out or input back to last menu or input exit to quit!洛阳 22 涧西区 23 西工区 24 老城区 25 洛龙区 26 吉利区 27 Please input back to last menu or input exit to quit!quit 28 29 Process finished with exit code 0
总结提高：
第二版代码相比第一版代码：
1、熟悉多级字典的写法；
2、加入 in 用法判断列表或字典的元素是否在其中，优化判断逻辑；
3、因为每级菜单都需要反复进入，引入循环嵌套；
4、可以通过引入循环标志位来同时跳出多级循环。