day 6 作业， 全国城市省、市、县三级菜单。

分析：此题目考虑到了字典，元组等数据，用字典比较好实现一些。

难点一：可随时返回上一级

思考中

为了方便先做三个省，每个省2个市，每个市1个县

难点二：随时退出程序。

思考中。

china_city = {
    "河北":{
            "石家庄":{
                        "栾城","正定"
                    },
            "衡水":{
                    "枣强","武邑"
                    }
            },
    "黑龙江省":{
            "哈尔滨":{
                "五常","木兰"
                    },
            "佳木斯":{
                "同江","东风"
                    }
                 },
    "广西省":{
            "南宁":{
                "江南","马山"
                    },
            "玉林":{
                "玉州","兴业"
            }
    }
}

def city_print(sheng,shi):
    sheng_namber = 0
    sheng_key = list(china_city.keys())

    if sheng == 0 and shi == 0:
        for i in china_city.keys():
            print(i)
    elif sheng !=0 and shi ==0 :
        sheng_zhi = sheng_key[sheng-1]
        for i in china_city[sheng_zhi].keys():
            print(i)
        shiqu = int(input("请输入你要查询的市区编码》》》"))
        if shiqu>=1 and shiqu<3:
            shi_zhi = china_city[sheng_zhi]
            shi_key = list(shi_zhi.keys())
            print(shi_zhi[shi_key[shiqu -1]])
        else:
            print("看好在选择哦,请重新选择")
judge = True
while judge == True:
    print("欢迎使用全国城市遍历系统！".center(50,"*"))
    for i in china_city.keys():
        print(i)
    shengfen = int(input("请输入你要查询的省份编码》》》"))
    shiqu = 0
    city_print(shengfen,shiqu)

第一个版本

目前退出还没写

china_city = {
    "河北":{
            "石家庄":{
                        "栾城","正定"
                    },
            "衡水":{
                    "枣强","武邑"
                    }
            },
    "黑龙江省":{
            "哈尔滨":{
                "五常","木兰"
                    },
            "佳木斯":{
                "同江","东风"
                    }
                 },
    "广西省":{
            "南宁":{
                "江南","马山"
                    },
            "玉林":{
                "玉州","兴业"
            }
    }
}
def quits():
    import os
    print("感谢使用，再见！")
    os._exit(0)
def city_print(sheng,shi):
    sheng_namber = 0
    sheng_key = list(china_city.keys())

    if sheng == 0 and shi == 0:
        for i in china_city.keys():
            print(i)
    elif sheng !=0 and shi ==0 :
        sheng_zhi = sheng_key[sheng-1]
        for i in china_city[sheng_zhi].keys():
            print(i)
        shiqu = int(input("请输入你要查询的市区编码,退出请输入123》》》"))
        if shiqu>=1 and shiqu<3:
            shi_zhi = china_city[sheng_zhi]
            shi_key = list(shi_zhi.keys())
            print(shi_zhi[shi_key[shiqu -1]])
        elif shiqu == 123:
            quits()
        else:
            print("看好在选择哦,请重新选择")
judge = True
while judge == True:
    print("欢迎使用全国城市遍历系统！".center(50,"*"))
    for i in china_city.keys():
        print(i)
    shengfen = int(input("请输入你要查询的省份编码,退出请输入123》》》"))
    shiqu = 0
    if shengfen == 123:
        quits()
    city_print(shengfen,shiqu)