Coding issue

[cvsae]

You can use dict to store usernames and passwords instead of list, and save dict to a file and load it each time when you run the *program check my example bellow

import json
import os 


auth_file = "auth.json"
auth = None



def loadAuth():
    if os.path.isfile(auth_file):
        return eval(open(auth_file).read())
    return {}

def saveAuth():
    json.dump(auth, open(auth_file, 'wt'))


if __name__ == '__main__':
    auth = loadAuth()

    operation = input('Login in or new user: ')

    if operation == 'login':
        username = input('username: ')
        password = input('password: ')

        if username in auth.keys() and auth[username] == password:
            print('Access granted')
        else:
            print('Access Denied - Wrong username or password')

    elif operation == 'new user':
        username = input('New username: ')
        password = input('New password: ')
        password_conf = input('confirm password: ')

        if password == password_conf:
            if username not in auth.keys():
                auth[username] = password
                saveAuth()
                auth == loadAuth()
                print('Welcome ' + username)
                print (username,auth[username])
            else:
                print ("Username already exists")