python作业设计：多级菜单，并可依次进入各级子菜单

'''作业三：多级菜单
三级菜单
可依次选择进入各子菜单
所需新知识点：列表、字典
'''

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("选择进入1层>>>:")
    if choice in data:
        while not exit_flag:
            for i2 in data[choice]:
                print("\t",i2)
            choice2 = input("选择进入2层>>>:")
            if choice2 in data[choice]:
                while not exit_flag:
                    for i3 in data[choice][choice2]:
                        print("\t\t", i3)
                    choice3 = input("选择进入4层>>>:")
                    if choice3 in data[choice][choice2]:
                        for i4 in data[choice][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