def register():
    while 1:
        username = input(‘輸入用戶名:‘)
        passwd = input(‘輸入密碼:‘)
        with open(‘homework/a.txt‘, ‘r+‘, encoding=‘utf-8‘) as f:
            for item in f:
                if username == item.split("\t")[0]:
                    print("用戶名存在,請重新輸入")
                    break
            else:
                f.write(username + "\t" + passwd + "\n")
                return
def login():
    index = 3
    while index > 0:
        name = input("請輸入用戶名:")
        passwd = input("輸入密碼:")
        with open(‘homework/a.txt‘, ‘r‘, encoding=‘utf-8‘) as f:
            for item in f:
                if name == item.split("\t")[0] and passwd == item.split(‘\t‘)[-1].strip():
                    print("恭喜您登陸成功")
                    return
            else:
                print("用戶名密碼錯誤,請重新登錄")
                index -= 1

if __name__ == "__main__":
    register()
    login()

寫一個函數完成三次登陸功能，再寫一個函數完成註冊功能