Python只读取CSV文件的第一行

Question

我相信这很简单，但它让我发疯。 代码仅读取 CSV 文件的第一行。 如果我在 CSV 顶部输入名称，它会要求输入密码。 如果我输入列表中的任何其他人，它会转到“您当前未注册”。 我想不通为什么？

with open('members.csv', 'r') as mem_login:
    login_reader = csv.reader(mem_login)
    for row in login_reader:
        if member in row:
            password = input('Please enter password...  ').lower()
            if password in row:
                print('Welcome ' + member.capitalize() + ', login successful!')
                sys.exit()
        else:
            reg_now = input('You are not currently registered. Would you like to sign-up now? Y or N   ').lower()

Answer 1

您的else案例附加到if member in row: ，因此如果第一row不包含member ，您会立即假定它们未注册。 Dedent 一行以将其附加到for循环，因此else块仅在for循环运行完成而没有break才会触发：

# newline='' is mandatory for csv module to handle dialect's newline conventions
# mode defaults to 'r', so you don't need to use it
with open('members.csv', newline='') as mem_login:
    # Unpack to username and userpass, and test individually, 
    # so user names are not their own passwords
    for username, userpass in csv.reader(mem_login): # One-lined creation of reader since it's only needed for loop
        if member == username:
            password = input('Please enter password...  ').lower()
            if password == userpass:
                print('Welcome ' + member.capitalize() + ', login successful!')
                break  # break bypasses the for's else block
    else:
        # Only runs if break not executed
        reg_now = input('You are not currently registered. Would you like to sign-up now? Y or N   ').lower()

我做了一些其他小的修复/改进（所有评论），但最大的变化是else块的 dedent 将它附加到for循环，而不是if 。

注意：即使经过我的更改，这也存在严重缺陷（无壳密码、明文密码），因此切勿将其用于真实用户身份验证。