How to make username update immediately rather than re-running program

Question

This program works to check usernames and passwords to let a user in. However, at the end where I am adding a new user, I want the user to immediately be able to try to import their newly created username and password so they can enter the program, without re-running after their username and password are added to the database. However, this code is returning the error "list index is out of range"

STAGE 1: Opening the files and grabbing data

filename1 = "c:\Users\Anna Hamelin\Documents\Python Scripts\SourceCode\Project2\usernames.txt" file = open(filename1, "r")

#Usernames
users = file.read()
usernameslist = [line.strip() for line in open("c:\\Users\\Anna Hamelin\\Documents\\Python Scripts\\SourceCode\\Project2\\usernames.txt")]
#print(users)                #Check file
#print(usernameslist)       #Check usernames list
file.close()

filename2 = "c:\\Users\\Anna Hamelin\\Documents\\Python Scripts\\SourceCode\\Project2\\passwords.txt"
file = open(filename2, "r")

#Passwords
passwords = file.read()
passwordslist = [line.strip() for line in open("c:\\Users\\Anna Hamelin\\Documents\\Python Scripts\\SourceCode\\Project2\\passwords.txt")]
#print(passwords)            #Check file
#print(passwordslist)       #Check passwords list
file.close()

#Compile the usernames and passwords lists for easy checking
#compiled_list = list(zip(usernameslist,passwordslist))
#print(compiled_list)

#Scores
filename3 = "c:\\Users\\Anna Hamelin\\Documents\\Python Scripts\\SourceCode\\Project2\\scores.txt"
file = open(filename3, "r")

scores = file.read()
scoreslist = [line.strip() for line in open("c:\\Users\\Anna Hamelin\\Documents\\Python Scripts\\SourceCode\\Project2\\scores.txt")]
#print(scores)           #Check file
#print(scoreslist)       #Check scores
file.close()

#STAGE 2
#Print Welcome/Intro message

response = input("-"*50 + "\nWelcome! Do you have an account (y/n)? ")
print("-"*50)

#If user has an account:
if response == "y":
    #Create a login function:
    #def login():
        goodlogin = False
        username = input("Please enter your username: ")
        password = input("Please enter your password: ")  
        for id in range(len(usernameslist)):
            if username == usernameslist[id] and password == passwordslist[id]:
                goodlogin = True 
                
        if goodlogin:
            print(print_in_green + "Access granted!" + print_default)
        else:
            print(print_in_red + "Incorrect Login credentials, please try again." + print_default)
    #login()

#If user does not have account:
else: 
    newusername = input("What is your new username? ")
    newpassowrd = input("What is your new password? ")
    file = open(filename1, "a")
    file.write("\n" + newusername)
    file = open(filename2, "a")
    file.write("\n" + newpassowrd)
    file.close
    print("Now that you have created an account, please continue.")
    goodlogin = False
    username = input("Please enter your username: ")
    password = input("Please enter your password: ")  
    for id in range(len(usernameslist)):
        if username == usernameslist[id] and password == passwordslist[id]:
                goodlogin = True 
                
    if goodlogin:
            print(print_in_green + "Access granted!" + print_default)
    else:
            print(print_in_red + "Incorrect Login credentials, please try again." + print_default)

Answer 1

You can abstract that interaction logic out into a loop. You can also remove a bunch of code with you use the with option of opening/closing files. Here's a prototype to keep users and passwords updated.

Your authentication is .... not safe haha, since multiple users can have the same password etc. I would create a hash out of the combination of the user and password, but thats a different story :)

def interact(user_names_ls, passwords_ls):
    goodlogin = False
    username = raw_input("Please enter your username: ")
    password = raw_input("Please enter your password: ")
    if username in user_names_ls and password in passwords_ls:
        goodlogin = True

    if goodlogin:
        print( "Access granted!")
    else:
        print("Incorrect Login credentials, please try again.")
        interact(user_names_ls, passwords_ls)


usernames_file_path = "usernames.txt"
with open(usernames_file_path, "r") as f:
    user_names_ls = f.readlines()
    user_names_ls = [user.rstrip() for user in user_names_ls]

passwords_file_path = "passwords.txt"
with open(passwords_file_path, "r") as f:
    passwords_ls = f.readlines()
    passwords_ls = [password.rstrip() for password in passwords_ls]


print("-"*50)
end_interaction = False

while not end_interaction:
    response = raw_input("-" * 50 + "\nWelcome! Do you have an account (y/n) [q to quit]? ")

    if response == "q":
        end_interaction = True

    #If user has an account:
    if response == "y":
        interact(user_names_ls, passwords_ls)

    #If user does not have account:
    else:
        newusername = raw_input("What is your new username? ")
        newpassowrd = raw_input("What is your new password? ")

        # here's where we can update our user and password cache
        user_names_ls.append(newusername)
        passwords_ls.append(newpassowrd)

# officially update the 'databases'
with open(usernames_file_path, "w") as f:
    user_names_ls = f.writelines(user_names_ls)


with open(usernames_file_path, "w") as f:
    passwords_ls = f.writelines(passwords_ls)

Sample interaction:

Welcome! Do you have an account (y/n) [q to quit]? n
What is your new username? he
What is your new password? 99
--------------------------------------------------
Welcome! Do you have an account (y/n) [q to quit]? y
Please enter your username: he
Please enter your password: 99
Access granted!
--------------------------------------------------
Welcome! Do you have an account (y/n) [q to quit]? 

btw - I used raw_input here but you can just swap that with input

Answer 2

I added a couple of functions to reduce code reuse. Also I load the usernames and passwords in the login_user function so it always gets the latest copy.

users_path = "c:\\Users\\Anna Hamelin\\Documents\\Python Scripts\\SourceCode\\Project2\\usernames.txt"
passwords_path = "c:\\Users\\Anna Hamelin\\Documents\\Python Scripts\\SourceCode\\Project2\\passwords.txt"
scoreslist_path = "c:\\Users\\Anna Hamelin\\Documents\\Python Scripts\\SourceCode\\Project2\\scores.txt"


def get_file_contents(file_path):
    return [line.strip() for line in open(file_path)]

scoreslist = get_file_contents(scoreslist_path)

def add_file_contents(file_path, contents):
    with open(file_path, "a") as file:
        file.write(contents)

def login_user(new_account=False):
    usernameslist = get_file_contents(users_path)
    passwordslist = get_file_contents(passwords_path)

    if new_account:
        response = 'y'
    else:
        response = input("-"*50 + "\nWelcome! Do you have an account (y/n)? ")
        print("-"*50)

    #If user has an account:
    if response == "y":
            goodlogin = False
            username = input("Please enter your username: ")
            password = input("Please enter your password: ")
            for id in range(len(usernameslist)):
                if username == usernameslist[id] and password == passwordslist[id]:
                    goodlogin = True

            if goodlogin:
                print("Access granted!")
            else:
                print("Incorrect Login credentials, please try again.")

    #If user does not have account:
    else:
        newusername = input("What is your new username? ")
        newpassword = input("What is your new password? ")
        add_file_contents(users_path, '\n' + newusername)
        add_file_contents(passwords_path, '\n' + newpassword)
        login_user(new_account=True)

login_user()