python-三级菜单

'''
程序: 三级菜单

要求:

打印省、市、县三级菜单
可返回上一级
可随时退出程序
'''

info = {
    '北京':{
        '昌平':{
            '沙河':["oldboy","test"],
            '天通苑':["我爱我家","链家地产"]
        },
        '朝阳':{
            '望京':["奔驰","陌陌"],
            '国贸':["CICC","HP"]
        },
        '海淀':{}
    },
    '上海':{
        '浦东':[]
    },
    '广州':{},
    '深圳':{}
}

exit_flag = False

while not exit_flag:
    for i in info:
        print(i)
    user_choice = input("你的选择是1>>>")
    if user_choice in info:
        while not exit_flag:
            for i2 in info[user_choice]:
                print("\t",i2)
            user_choice2 = input("你的选择是2>>>")
            if user_choice2 in info[user_choice]:
                while not exit_flag:
                    for i3 in info[user_choice][user_choice2]:
                        print("\t\t",i3)
                    user_choice3 = input("你的选择是3>>>")
                    if user_choice3 in info[user_choice][user_choice2]:
                        while not exit_flag:
                            for i4 in info[user_choice][user_choice2][user_choice3]:
                                print("\t\t\t",i4)
                            user_choice4 = input("最后一层，请输入“b”返回>>>")
                            if user_choice4 == "b":
                                break
                            elif user_choice4 == "q":
                                exit_flag = True
                    elif user_choice3 == "b":
                        break
                    elif user_choice3 == "q":
                        exit_flag = True
            elif user_choice2 == "b":
                break
            elif user_choice2 == "q":
                exit_flag = True
    elif user_choice == "b":
        break
    elif user_choice == "q":
        exit_flag = True