练习一个三级菜单

首先按照自己的想法写出来

menu = {
   '北京': {
      '朝阳': {
         '国贸': {
            'CCC': {},
            'HP': {},
            'CCTV': {},
         },
      },
      '昌平': {
         '昌平': {
            '天通苑': {},
         },
      },
      '海淀': {
         '默默': {
            '陌陌': {},
         },
         '五道口': {
            '快手': {},
         }
      },
   },
   '上海': {
      '浦东': {
         '陆家嘴': {
            '高盛': {},
         },
         '外滩': {},
      },
      '闵行': {},
   },
   '山东': {
      '济南': {},
      '德州': {
         '乐林': {
            '订看':{},
         },
      },
   },
}
break_flag = False
exit_flag = False
while not break_flag and not exit_flag :
   for key in menu:
      print(key)
   choice = input("1>>:").strip()
   if choice == 'b':
      break_flag = True
   if choice == 'q':
      exit_flag = True
   if choice in menu:
      while not break_flag and not exit_flag:
         for key2 in menu[choice]:
            print(key2)
         choice2 = input("2>>:").strip()
         if choice2 == 'b':
            break_flag = True
         if choice == 'q':
            exit_flag = True
         if choice2 in menu[choice]:
            while not break_flag and not exit_flag:
               for key3 in menu[choice][choice2]:
                  print(key3)
               choice3 = input("3>>:").strip()
               if choice2 == 'b':
                  break_flag = True
               if choice == 'q':
                  exit_flag = True
               if choice3 in menu[choice][choice2]:
                     for key4 in menu[choice][choice2][choice3]:
                        print(key4)
            else:
               break_flag = False

         else:
            break_flag = False
   else:
      break_flag = False
==========================================
如果上面的完成了！可以试试优化  因为看上去上面的代码很多地方都是重复的

menu = {
   '北京': {
      '朝阳': {
         '国贸': {
            'CCC': {},
            'HP': {},
            'CCTV': {},
         },
      },
      '昌平': {
         '昌平': {
            '天通苑': {},
         },
      },
      '海淀': {
         '默默': {
            '陌陌': {},
         },
         '五道口': {
            '快手': {},
         }
      },
   },
   '上海': {
      '浦东': {
         '陆家嘴': {
            '高盛': {},
         },
         '外滩': {},
      },
      '闵行': {},
   },
   '山东': {
      '济南': {},
      '德州': {
         '乐林': {
            '订看':{},
         },
      },
   },
}
current_layer = menu
parent_layers = []
while True:
   for key in current_layer:
      print(key)
   choice = input(">>:").strip()
   if len(choice) == 0:continue
   elif choice in current_layer:
      parent_layers.append(current_layer)
      current_layer =current_layer[choice]
   elif choice == 'b':
      if parent_layers:
         current_layer = parent_layers.pop()
   else:
      print("input error!")