def play_again(self):
        """Gives user the chance to quit the program or continue."""
        while True: # until user enters valid input
            self.refresh()
            option = raw_input("Play again (enter) or n? ").strip().lower()
            if not option:
                self.message = ''
                return
            elif option in ["no", 'n']:
                import sys
                sys.exit()
            else:
                self.message = "That's not a valid option!"
Gives user the chance to quit the program or continue.
recipes/Python/578563_Tic_Tac_Toe_console_game/recipe-578563.py