Python脚本无法读取用户名文件内容，此前正常现突发故障求助

脚本无法识别用户名文件中的名称。

脚本可以找到该文件，只要稍微修改路径中的名称程序就无法运行，但无论如何都无法读取文件中的内容——我编写程序时它还能正常工作，现在突然失效了，文件位置也没有变化。
附：我不知道怎么在Stack Overflow上正确格式化代码

原始代码 #

filen = 'C:\Users\fabby\Documents\Extra Things I Might Need\Port Folio Stuff\Python\usernames'
usern = open(filen, 'r')
userr = input("Enter your Username: ")
ass = input("Enter your Password: ")


def func():
    user = input("Enter new Username: ")
    passs = input("Enter new Password: ")
    passs1 = input("Confirm password: ")

    if passs != passs1:
        print("Passwords do not match!")
    else:
        if len(passs) <= 6:
            print("Your password is too short, restart:")

        elif user in usern:
            print("This username already exists")

        else:
            usern = open(filen, "a")
            usern.write(user+", "+passs+"\n")
            print("Success!")

while True:
    if userr not in usern:
        again = input("This username does not exist, would you like to try again? ")
        if again == ("No"):
            func()
        elif again == ("no"):
            func()
        elif again == ("Yes"):
            print("Try again:")
            userr = input("Enter your Username: ")
            ass = input("Enter your Password: ")
        elif again == ("yes"):
            print("Try again:")
            userr = input("Enter your Username: ")
            ass = input("Enter your Password: ")
        elif userr in usern:
            print("Good, you have entered the zone")

1. 路径转义错误 #

Windows路径里的\在Python字符串中是转义字符，比如\U会被解析为Unicode转义，直接导致路径识别异常。三种解决方式：

• 用双反斜杠替换：filen = 'C:\\Users\\fabby\\Documents\\Extra Things I Might Need\\Port Folio Stuff\\Python\\usernames'
• 用原始字符串（引号前加r）：filen = r'C:\Users\fabby\Documents\Extra Things I Might Need\Port Folio Stuff\Python\usernames'
• 用正斜杠替代：filen = 'C:/Users/fabby/Documents/Extra Things I Might Need/Port Folio Stuff/Python/usernames'

2. 文件内容读取逻辑错误 #

你直接用user in usern是检查字符串是否在文件对象里，而非文件内容中。必须先读取文件内容才能做判断：

• 读取所有内容并拆分用户列表：with open(filen, 'r') as f: existing_users = [line.split(',')[0].strip() for line in f]，之后用user in existing_users做检查
• 注意：文件指针读取一次后会停在末尾，重复读取前需要重新打开文件或移动指针

3. 文件操作规范 #

直接open()文件后不关闭会导致资源泄漏，建议用with语句自动管理文件生命周期，避免此类问题。

修正后的完整代码 #

filen = r'C:\Users\fabby\Documents\Extra Things I Might Need\Port Folio Stuff\Python\usernames'

def func():
    user = input("Enter new Username: ")
    passs = input("Enter new Password: ")
    passs1 = input("Confirm password: ")

    if passs != passs1:
        print("Passwords do not match!")
        return
    if len(passs) <= 6:
        print("Your password is too short, restart:")
        return
    
    # 读取现有用户名列表
    with open(filen, 'r') as f:
        existing_users = [line.split(',')[0].strip() for line in f.readlines()]
    if user in existing_users:
        print("This username already exists")
        return
    
    # 写入新用户信息
    with open(filen, "a") as f:
        f.write(f"{user}, {passs}\n")
        print("Success!")

while True:
    userr = input("Enter your Username: ")
    ass = input("Enter your Password: ")
    
    # 验证用户是否存在
    with open(filen, 'r') as f:
        existing_users = [line.split(',')[0].strip() for line in f.readlines()]
    if userr not in existing_users:
        again = input("This username does not exist, would you like to try again? ")
        if again.lower() == "no":
            func()
            break
        elif again.lower() == "yes":
            print("Try again:")
        else:
            print("Invalid input, please enter Yes or No")
    else:
        print("Good, you have entered the zone")
        break

Stack Overflow代码格式化方法 #

• 单行代码：用单个反引号包裹，比如print("hello world")
• 多行代码块：在代码前后各加三个反引号（），开头的反引号后可指定语言（比如python），实现语法高亮

内容的提问来源于stack exchange，提问作者Noodle Head117