Python登录系统读取txt账号密码触发ValueError解包错误求助

问题复现 #

编写基于Python的账号登录系统时，注册逻辑可正常将邮箱、SHA256加密后的密码写入database.txt文件，但登录环节执行到读取存储凭证的代码行时，抛出如下异常：
ValueError: too many values to unpack (expected 2)
原实现完整代码如下：

import hashlib
def signup():
    email = input("Enter an email address: ")
    pwd = input("Enter a password: ")
    conf_pwd = input("Confirm your password: ")
    if conf_pwd == pwd:
        enc = conf_pwd.encode()
        hash1 = hashlib.sha256(enc).hexdigest()
        with open(r'D:\Python Programs\Login\database.txt', "a") as f:
             f.write(email + "\n")
             f.write(hash1 + "\n")
        f.close()
        print("You have registered successfully!")
    else:
        print("Password is not same as above! \nPlease try again")
        signup()
def login():
    email = input("Enter email: ")
    pwd = input("Enter password: ")
    auth = pwd.encode()
    auth_hash = hashlib.sha256(auth).hexdigest()
    with open(r'D:\Python Programs\Login\database.txt', "r") as f:
        stored_email, stored_pwd = f.read().split("\n")
    f.close()
    if email == stored_email and auth_hash == stored_pwd:
         print("Logged in Successfully!")
    else:
         print("Login failed! \nPlease try again")
         login()
def welcome():
    print("Welcome to the [Insert Game Name Here]")
    HaveAccount = input("Have you made an account before? (Y/N): ")
    if HaveAccount == ("Y"):
        login()
    elif HaveAccount == ("N"):
        signup()
    else:
        print("Please enter either 'Y' or 'N'")
        welcome()

welcome()

报错原因 #

• 注册逻辑用追加模式"a"写入文件，每注册1个账号就会往txt里新增2行内容：第一行是邮箱，第二行是密码哈希。只要注册账号数≥2，文件内的总行数就会超过2行。
• 登录逻辑里f.read().split("\n")会把整个文件的所有内容按换行符切割成列表，比如2个账号就会切割出至少4个有效元素+1个文件末尾空字符串，总长度远大于2，此时强行把列表拆包赋值给stored_email, stored_pwd两个变量，就会触发值过多的拆包错误。
• 额外代码隐患：使用with open()上下文管理器操作文件时，会自动完成文件关闭，不需要手动调用f.close()；用递归调用login()/signup()处理输入错误、登录失败的重试逻辑，多次重试后会触发栈溢出，改用循环实现更稳妥。

修复方案 #

调整登录时的文件读取逻辑，逐行遍历存储的所有账号凭证做匹配，同时修正冗余代码和递归问题，补充重复注册、数据库文件不存在的边界判断，修复后代码如下：

import hashlib
import os

DB_PATH = r'D:\Python Programs\Login\database.txt'

def signup():
    while True:
        email = input("Enter an email address: ")
        pwd = input("Enter a password: ")
        conf_pwd = input("Confirm your password: ")
        if conf_pwd != pwd:
            print("Password is not same as above! \nPlease try again")
            continue
        enc = conf_pwd.encode()
        hash1 = hashlib.sha256(enc).hexdigest()
        # 检查邮箱是否已注册
        is_exist = False
        if os.path.exists(DB_PATH):
            with open(DB_PATH, "r") as f:
                lines = [line.strip() for line in f if line.strip()]
                for i in range(0, len(lines), 2):
                    if lines[i] == email:
                        is_exist = True
                        break
        if is_exist:
            print("This email has been registered! Please try another or login.")
            return
        with open(DB_PATH, "a") as f:
             f.write(email + "\n")
             f.write(hash1 + "\n")
        print("You have registered successfully!")
        return

def login():
    while True:
        email = input("Enter email: ")
        pwd = input("Enter password: ")
        auth = pwd.encode()
        auth_hash = hashlib.sha256(auth).hexdigest()
        login_success = False
        if not os.path.exists(DB_PATH):
            print("No account found! Please sign up first.")
            return
        with open(DB_PATH, "r") as f:
            lines = [line.strip() for line in f if line.strip()]
        # 每两行一组匹配账号密码
        for i in range(0, len(lines), 2):
            stored_email = lines[i]
            stored_pwd = lines[i+1]
            if email == stored_email and auth_hash == stored_pwd:
                login_success = True
                break
        if login_success:
            print("Logged in Successfully!")
            return
        print("Login failed! \nPlease try again")

def welcome():
    print("Welcome to the [Insert Game Name Here]")
    while True:
        have_account = input("Have you made an account before? (Y/N): ").strip()
        if have_account == "Y":
            login()
            break
        elif have_account == "N":
            signup()
            break
        else:
            print("Please enter either 'Y' or 'N'")

welcome()

内容的提问来源于stack exchange，提问作者Iron_Ryan19