四级菜单实现（Python）

menu_dict = {
     ‘山东‘ : {
         ‘青岛‘ : {
             ‘四方‘:{‘兴隆路‘,‘平安路‘,‘杭州路‘},
             ‘黄岛‘:{},
             ‘崂山‘:{}
         },
         ‘济南‘ : {
             ‘历城‘:{},
             ‘槐荫‘:{},
             ‘高新‘:{}
         },
     },
     ‘江苏‘ : {
         ‘苏州‘ : {
             ‘沧浪‘:{},
             ‘相城‘:{},
             ‘平江‘:{}
         },
         ‘南京‘ : {
             ‘白下‘:{},
             ‘秦淮‘:{},
             ‘浦口‘:{}
         }
     }
}

current_layer = menu_dict
parent_layers = []#把不同层级的字典保存在列表中（列表中嵌套字典)[menu_dict,menu_dict[省]，。。。。],到最后一层的时候列表是下面这个样子
#parent_layers[0]={‘山东‘: {‘青岛‘: {‘四方‘: {‘杭州路‘, ‘兴隆路‘, ‘平安路‘}, ‘黄岛‘: {}, ‘崂山‘: {}}, ‘济南‘: {‘历城‘: {}, ‘槐荫‘: {}, ‘高新‘: {}}}, ‘江苏‘: {‘苏州‘: {‘沧浪‘: {}, ‘相城‘: {}, ‘平江‘: {}}, ‘南京‘: {‘白下‘: {}, ‘秦淮‘: {}, ‘浦口‘: {}}}}

#parent_layers[1]={‘青岛‘: {‘四方‘: {‘杭州路‘, ‘兴隆路‘, ‘平安路‘}, ‘黄岛‘: {}, ‘崂山‘: {}}, ‘济南‘: {‘历城‘: {}, ‘槐荫‘: {}, ‘高新‘: {}}}

#parent_layers[2]={‘四方‘: {‘杭州路‘, ‘兴隆路‘, ‘平安路‘}, ‘黄岛‘: {}, ‘崂山‘: {}}while True:

    for key in current_layer:
        print(key)
    choice = input(">>:").strip()
    if len(choice) == 0:
        continue
    if 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("无此项")