Python之双色球选购和三级菜单问题

• 数据结构：
  menu = {
      ‘北京‘:{
          ‘海淀‘:{
              ‘五道口‘:{
                  ‘soho‘:{},
                  ‘网易‘:{},
                  ‘google‘:{}
              },
              ‘中关村‘:{
                  ‘爱奇艺‘:{},
                  ‘汽车之家‘:{},
                  ‘youku‘:{},
              },
              ‘上地‘:{
                  ‘百度‘:{},
              },
          },
          ‘昌平‘:{
              ‘沙河‘:{
                  ‘老男孩‘:{},
                  ‘北航‘:{},
              },
              ‘天通苑‘:{},
              ‘回龙观‘:{},
          },
          ‘朝阳‘:{},
          ‘东城‘:{},
      },
      ‘上海‘:{
          ‘闵行‘:{
              "人民广场":{
                  ‘炸鸡店‘:{}
              }
          },
          ‘闸北‘:{
              ‘火车站‘:{
                  ‘携程‘:{}
              }
          },
          ‘浦东‘:{},
      },
      ‘山东‘:{},
  }
  
  需求：
  可依次选择进入各子菜单
  可从任意一层往回退到上一层
  可从任意一层退出程序
  所需新知识点：列表、字典

代码一：

 exit_flag = False
while not exit_flag:
    for i in menu:
        print(i)
    choice1 = input("选择进入1>>:")
    if choice1 in menu:
        while not exit_flag:
            for i2 in menu[choice1]:
                print("\t", i2)
            choice2 = input("选择进入2>>:")
            if choice2 in menu[choice1]:
                while not exit_flag:
                    for i3 in menu[choice1][choice2]:
                        print("\t\t", i3)
                    choice3 = input("选择进入3>>:")
                    if choice3 in menu[choice1][choice2]:
                        for i4 in menu[choice1][choice2][choice3]:
                            print("\t\t", i4)
                        choice4 = input("最后一层，按b返回>>:")
                        if choice4 == "b":
                            pass
                        elif choice4 == "q":
                            exit_flag = True
                    if choice3 == "b":
                        break
                    elif choice3 == "q":
                        exit_flag = True
            if choice2 == "b":
                break
            elif choice2 == "q":
                exit_flag = True

代码二：（优化版本，代码缩减为15行）

current_layer = menu
parent_layer = []  # 将父级key值放入到列表中
flags = False  # 设置标志位
while not flags:
    for key in current_layer:
        print(key)
    choose = input("请选择，输入b返回上一级菜单，输入q退出菜单:").strip()  # 去除空格
    if choose in current_layer:
        parent_layer.append(current_layer)  # 将当前的状态放入列表中
        current_layer = current_layer[choose]
    elif choose == ‘b‘:
        if parent_layer:
            current_layer = parent_layer.pop()
    elif choose == ‘q‘:
        flags = True
    else:
        print(‘输入有误，请重新输入‘)