Python program just ends after a loop

Question

I am trying to make a logging in system with python. To login you must first register. After you have registered it stores it into a text file with the password in base64. Then if you login it asks for username and password which the password gets encoded into base64 and is checked against the text document. But when it searches for the password nothing happens. It just ends the program and goes to the shell. No traceback error or anything. It is as though the rest of the code is invisible. Code is below:

try:
    import linecache
    import base64
    import tkinter
    import time
    choice = ""
    def choose():
        choice = input("Would you liek to register or login: ")
        choice = choice.upper()
        if choice == "REGISTER":
            f = open("h.txt", "a")
            f.write("\n")
            print("Please enetr a username")
            username = input(">>> ")
            print("Please enter a password")
            passw = input(">>> ")
            print("\n"*100)
            passw_conf = input("Please enter your password again\n>>> ")
            print("\n"*100)
            if passw == passw_conf:
                print("Thank you for Registering")
                f.write(username + "\n")
                passw = base64.b64encode(passw.encode('utf-8'))
                passw = str(passw)[2:-1]
                f.write(passw + "\n")
                f.close()
                choose()
            else:
                print("Please choose register again as passwords do not match.")
        elif choice == "LOGIN":
            username = input("Please enter your username\n>>> ")
            passw = input("Please enter your password\n>>> ")

            x = 0
            with open("h.txt") as f:
                    lines = [line.rstrip('\n') for line in open('h.txt')]
            while lines[x] != username:

                print(lines[x])
                if lines == username:
                    print("Got it ;)")
                elif lines != username:
                    print("Not got it ;(")
            passw = base64.b64encode(passw.encode('utf-8'))
            passw = str(passw)[2:-1]
            if passw == lines:
                print("Logged in successfully")
            elif lines == "":
                print("Username not found!")
    choose()
except KeyboardInterrupt:
    print("Restarting....")
    time.sleep(8)
    print("\n"*100)
    choose()
    choose()

Answer 1

Executed once, we expect the first line should be username, this means, the while breaks at x=0 (while-start). Then the variable lines is a list, it does not equals to the password and it is not empty (no prints). Sorry the program does what you wrote!

Other things that I see:

• you are opening the file twice (with-statement + line below)
• The while-loop is not a loop (x+=1)
• if-statement after the while-statement can never be true (if lines[x] == username cannot work for lines[x] != username)

There is a simple way to debug this: print!

• one after each line of code
• showing variables you are using to control the flow (lines)

Answer 2

There are many problems with your code. It works only, if the first username in h.txt is the entered one, otherwise you have a infinite loop. Second, lines is a list, so never equal to passwd or "". Therefore nothing is printed.

It should look like this:

    username = input("Please enter your username\n>>> ")
    passw = input("Please enter your password\n>>> ")

    with open("h.txt") as f:
        lines = [line.rstrip('\n') for line in f]
    for line in lines:
        if line == username:
            user_password = next(lines)
            break
    else:
        print("Username not found!")
        return
    passw = base64.b64encode(passw.encode('utf-8'))
    passw = passw[2:-1]
    if passw == user_password:
        print("Logged in successfully")
    else:
        print("Wrong password")