Python只读取CSV文件的第一行

Question

I'm sure this is simple, but it's driving me nuts. Code only reads the first line of the CSV file. If I enter the name at the top of the CSV it asks for the password. If I enter any of the others in the list it goes to 'You are not currently registered'. I can't figure out why?

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

Your else case is attached to if member in row: , so if the first row doesn't contain the member , you immediately assume they're unregistered. Dedent it a line to attach it to the for loop, so the else block only fires if the for loop runs to completion without break ing:

# 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()

I made few other small fixes/improvements (all commented), but the big change is the dedent of the else block to attach it to the for loop, not the if .

Note: Even with my changes, this has serious flaws (caseless passwords, passwords in plaintext), so never use it for real user authentication.