跟文件结合的验证登陆

def login(username,password):    f = open("db","r",encoding="utf-8")    for line in f:        line = line.strip()#默认strip无参数：移除空格换行符；有参数：移除两侧指定的值        line_list = line.split("$$")        if user == line_list[0] and pwd == line_list[1]:            return True    return Falsedef register(username,password):    #注册用户#1打开文件2用户名密码    with open("db","a",encoding="utf-8") as f:        temp = "\n" + username + "$$" + password        f.write(temp)def user_exist(username):    #一行一行查找，若是用户名存在，returnTrue；False    with open("db","r",encoding="utf-8") as f:        for line in f:            line = line.strip()            line_list = line.split("$$")            if line_list[0] == username:                return True    return Falseprint("欢迎来到德莱联盟")inp = input("1:登陆；2:注册")if inp == "1":    user = input("请输入用户名:")    pwd = input("请输入密码:")    is_login = login(user,pwd)    if is_login:        print("登陆成功")    else:        print("登陆失败")elif inp == "2":    user = input("请输入用户：")    pwd = input("请输入密码：")    is_exist = user_exist(user)    if is_exist:        print("用户已存在，没法注册")    else:        register(user,pwd)        print("注册成功")