我如何让这个简单的python登录程序循环？

Question

this is my first time posting on stack overflow and I would be very appreciative if someone could help me with a simple loop function. This project is supposed to be for a group of 4 people, however I have been majorly let down and have had no support from my team.

Im a complete beginner to python and would be grateful for any help or suggestions.

I have tried to mess about and incorporate a loop but I feel very out of my depth.

The current program works and extracts the username and password in the .txt file as the format (username,password) however, it is the beginning of a quiz program. If an incorrect username/password is entered, the user is still able to begin the quiz.

login_username = input('username: ')
login_password = input('password: ')
found_username = False

with open('passwords.txt', 'r') as password_file:
    for line in password_file:
        username, password = line.strip().split(',')

        if login_username == username:
            found_username = True
            if login_password == password:
                print('success!')
            else:
                print('login failure!')
            break

if not found_username:
    print('username invalid')

I would be extremely grateful for any support available :)

Answer 1

You have a few different options. The most basic of which will keep asking for a password, as long the correct one is not already entered. This also means making minimal edits to the code you already have.

logged_in = False #Defines if user is logged in or not
while not logged_in:
    login_username = input('username: ')
    login_password = input('password: ')
    found_username = False

    with open('passwords.txt', 'r') as password_file:
        for line in password_file:
            username, password = line.strip().split(',')

            if login_username == username:
                found_username = True
                if login_password == password:
                    print('success!')
                    logged_in = True #We're not logged in, so loop will exit
                else:
                    print('login failure!')
                break

    if not found_username:
        print('username invalid')

This will keep repeating to ask for the username AND password , so a better version might be to take the username (and username check) into a different while loop.

Hope this helps!

Answer 2

First, I will input all the username and password into a dictionary Second, I use a while loop to keep asking the user to put into the correct username and password

found_username = False
user_dict = {}
#Add username and password into a user dictionary (or library)
with open('passwords.txt', 'r') as password_file:
    for line in password_file:
        username, password = line.strip().split(',')
        user_dict[username] = password
while found_username == False: #keep asking until correct username and password
    login_username = input('username: ')
    login_password = input('password: ')
    #Check input username and password
    for user in user_dict:
        if login_username == user: #check username
            no_username_found = False
            if login_password == user_dict[user]: #check password
                print('success!')
                found_username = True  #accept
                no_username_found = False
                break   #stop when password is correct
            else:
                print('login failure!') #wrong password
                found_username = False
                break  #stop when password is wrong
        else:
            no_username_found = True    

    if no_username_found == True: #check if usename is not found
        print('username invalid') 

print(found_username)