day2...三级菜单

#Author:walter
data = {
    '北京':{
        "昌平":{
            "沙河":["oldboy","test"],
            "天通苑":["链家地产","我爱我家"]
        },
        "朝阳":{
            "望京":["奔驰","陌陌"],
            "国贸":{"CICC","HP"},
            "东直门":{"Advent","飞信"},
        },
        "海淀":{},
    },
    '山东':{
        "德州":{},
        "青岛":{},
        "济南":{}
    },
    '广东':{
        "东莞":{},
        "常熟":{},
        "佛山":{},
    },
}
exit_flag = False
while not exit_flag:
    for i in data:
        print(i)

    choice = input("请选择进入1：")
    if choice in data:
        while not exit_flag:
            for j in data[choice]:
                print("\t",j)

            choice2 = input("请选择进入2：")
            if choice2 in data[choice]:
                while not exit_flag:
                    for k in data[choice][choice2]:
                        print("\t\t", k)

                    choice3 = input("请选择进入3：")
                    if choice3 in data[choice][choice2]:
                        while not exit_flag:
                            for l in data[choice][choice2][choice3]:
                                print("\t\t", l)

                            choice4 = input("最后一层，请按b返回>>：")
                            if choice4 == "b":
                                break
                            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