很高兴今天用PYTHON3写了三级菜单程序！

#!usrinenvpython
# -*- coding:utf - 8 -*9
# Author:Alex hua
university_list = {              # 大学列表
    "安徽省": {
        "合肥": ["中国科技大学", "合肥工业大学"],
        "安庆": ["安庆学院"],
        "阜阳": ["阜阳学院"]
    },
    "江苏省": {
        "南京": ["南京大学", "南京工业大学"],
        "南通": ["南通大学"],
        "苏州": ["苏州大学"],
    },
    "浙江省": {
        "杭州": ["浙江大学", "杭州电子科技大学"],
        "宁波": ["宁波大学"],
        "嘉兴": ["嘉兴学院"],
    }
}
flag = True
try_province = 0
try_city = 0
try_school = 0
while flag:
    if try_province<3:
        province_str1="欢迎进入沿海省份"
        print(province_str1.center(20,'-'))
        for province in university_list.keys():
            print(province)
        print("-----------------------------")
        province_input = input("请输入省份:")
        city_flag = True
        while city_flag:
            if try_city<3:
                if province_input.strip() in university_list:
                    print("欢迎进入：%s!" % (province_input,)) #赋值，一定要打逗号
                    city_str2 = "欢迎进入中国地区"
                    print(city_str2.center(20,'-'))
                    for city in university_list[province_input].keys():
                        print(city)
                    print("--------------------")
                    city_input=input("请输入中国城市：")
                    school_flag = True
                    while school_flag:
                        if try_school<3:
                            if city_input.strip() in university_list[province_input]:
                                print("欢迎进入: %s!" % (city_input,))
                                school_str3="欢迎进入中国学校"
                                print(school_str3.center(20,'-'))
                                for school in university_list[province_input][city_input]:
                                    print(school)
                                print("----------------------")
                                school_input=input("请输入学校名称")
                                if school_input.strip() in university_list:
                                    print("欢迎进入: %s!" % (school_input,))
                                    print("当前位置:%s--%s--%s" % (province_input, city_input, school_input,))
                                    print("已经结束了")
                                    flag =False
                                    city_flag=False
                                    school_flag=False
                                    break
                                else:
                                    print("你输入学校信息有误,请重新输入")
                                    try_school+=1
                            else:
                                print("你输入城市信息有误,请重新输入")
                                try_city+=1
                                school_flag = False
                        else:
                            print("输入超过三次，返回执行")
                            flag=False
                            city_flag=False
                            school_flag=False
                else:
                    print("输入省份信息有误,请重新输入")
                    try_province +=1
                    city_flag=False
            else:
                print("输入三次,返回执行")
                flag=False
                city_flag =False
    else:
        print("输入超过三次，返回执行")
        flag=False