import os
import time
def clearscreen(numlines=100):
    if os.name == "posix":
    # Unix/Linux/MacOS/BSD/etc
        os.system('clear')
    elif os.name in ("nt", "dos", "ce"):
    # DOS/Windows
        os.system('CLS')
    else:
    # Fallback for other operating systems.
        print '\n' * numlines


loop = 1
users = []

while loop == 1:
    clearscreen()
    print "Welcome to yerer's login screen"
    print " "
    choice = input("1. Login\n2. Create account\n3. Exit\nq")
    if choice == 2:
        clearscreen()
        print "New Account"
        users.append([raw_input("Username: "), raw_input("Password: ")])
    if choice == 1:
        clearscreen()
        print "Existing User"
        username = raw_input("Username: ")
        password = raw_input("Password: ")
        if [username, password] in users:
            print "Welcome"
            loop == 0
        else:
            clearscreen()
            print "Username and password combination not recognized\n"
            time.sleep(3)
    if choice == 0:
        print "Goodbye"
        loop = 0