python实现简单的购物车

import json,time
userinfo={"lanfei":
              { "passwd":"lanfei",
                "salary":3000,
                "buy_commodity":{  "time":None,
                                    "commodity_name":None,
                                    "price":None,},
                "shopping_cart":{
                                    "commodity_name":None,
                                    "price":None,}
               }
          }
commodity_list={"ipad":{"price":100,"orign_place":"北京"}}
def import_to_file():
    try:
        f1=open(r"F:\userinfo.txt",'w',encoding="utf-8")
        f2=open(r"F:\commodity.txt",'w',encoding="utf-8")
        json.dump(userinfo,f1)
        json.dump(commodity_list,f2)
        f1.close()
        f2.close()
    except FileNotFoundError as e:
        print(e)
    except Exception as e:
        print(e)
def export_from_file():
    global userinfo
    global commodity_list
    global commodity_list
    try:
        f1=open(r"F:\userinfo.txt",'r',encoding="utf-8")
        f2=open(r"F:\commodity.txt","r",encoding="utf-8")
        userinfo=json.load(f1)
        commodity_list=json.load(f2)
        f1.close()
        f2.close
    except FileNotFoundError as e:
        print(e)
    except Exception as e:
        print(e)
def creat_user(name,passwd):
    export_from_file()
    if name in userinfo.keys():
        print("usernam has exist!")
        name=input("rewrite your username:")
        passswd=input("rewrite your userpassswd:")
        creat_user(name,passwd)
    else:
        userinfo.setdefault(name,{"passwd":passwd,"salary":None})
        return True
def add_commmdity(mount):
    print("商品添加".center(30))
    print('-'*35)
    for i in range(mount):
        commodity=input("输入要添加的商品:")
        price=eval(input("输入商品的价格:"))
        info=input("输入商品的信息:")
        commodity_list.setdefault(commodity,{"price":price,"orign_place":None})
        if commodity not in commodity_list.keys():
            print("%s添加失败"%commodity)
    else:
        print("全部添加成功")
        import_to_file()

def authentication(name,passwd):
    export_from_file()
    if name in userinfo.keys():
        if passwd==userinfo[name]["passwd"]:
            return True
        else:
            return False
    else:
        return False
def shopping(name):
    while True:
        print("商品列表".center(30))
        print("-" * 35)
        for index,item in commodity_list.items():
            print("%s:\n\t%s\n\t%s"%(index,item["price"],item["orign_place"]))
        commodity_name=input("输入您想要购买的商品名称:")
        while commodity_name not in commodity_list.keys():
            commodity_name=input("商品不存在,请重新输入:")
        price=commodity_list[commodity_name]["price"]
        if userinfo[name]["salary"]>=price:
            ack=input("确认购买(y/n):")
            if ack=="y":
                userinfo[name]["salary"]-=price
                userinfo[name].setdefault("buy_commodity",{"time":time.ctime(),"price":price,"commdity_name":commodity_name})
                print("购买成功,您的余额:%s"%userinfo[name]["salary"])
            elif ack=='no':
                continue
            elif ack=='exit':
                break
        else:
            print("余额不足,请充值！")
            ack=input("是否退出程序(y/n)：")
            if ack=="y":
                exit()
            else:
                continue
def user_login_interface():
    function=input("登录输入login，注册输入regist:")
    if function !="login" and function != "regist":
        print("输入错误！")
    name=input("username:")
    passwd=input("userpassswd:")
    if function=="login":
        if authentication(name,passwd)==True:
            print("login successfully!")
            shopping(name)
        else:
            print("username or userpasswd error!")
    elif function=="regist":
        if creat_user(name,passwd)==True:
            import_to_file()
            print("regist sucessfully!")
def merchant_login_interface():
    function=input("登录输入login，注册输入regist:")
    if function !="login" and function != "regist":
        print("输入错误！")
        exit()
    name=input("username:")
    passwd=input("userpassswd:")
    if function=="login":
        if authentication(name,passwd)==True:
            print("login successfully!")
            mount=eval(input("输入添加商品的数目:"))
            add_commmdity(mount)
        else:
            print("username or userpasswd error!")
    elif function=="regist":
        if creat_user(name,passwd)==True:
            import_to_file()
            print("regist sucessfully!")
#user_login_interface()
merchant_login_interface()