定义函数完成注册和登录功能

def register():
    while 1:
        import os
        check = input("退出注册请按Q或q")
        if check.upper() == "Q":
            break
        else:
            username = input("请输入用户名:")
            password = input("请输入用户名密码（禁止使用“_”） :")
            with open("11.txt", mode="r", encoding="utf-8") as f1,\
                open("11.txt_副本", mode="w", encoding="utf-8") as f2:
                count = 1
                for line in f1:
                    f2.write(line)
                    s = line.strip().split("_")
                    if username == s[0]:
                        count = count +1
                if count > 1:
                    print("用户名已被注册")
                else:
                    f2.write(username + "_" + password + "\n")
        os.remove("11.txt")
        os.rename("11.txt_副本", "11.txt")

def login():
    while 1:
        check = input("退出登录请按Q或q：")
        if check.upper() == "Q":
            break
        else:
            username = input("请输入用户名：")
            password = input("请输入密码：")
            with open("11.txt", mode="r", encoding="utf-8") as f:
                count = 0
                for line in f:
                    u, p = line.strip().split("_")
                    if username == u and password == p:
                        count = count +1
                if count == 1:
                    print("登录成功")
                else:
                    print("密码或用户名错误，请重新登录！")
register()
login()