def free_dead(cls):
        """Removes all threads that return FALSE on isAlive() from the running_threads list """
        for th in cls.running_threads[:]:
            if th[0].isAlive() == False:
                cls.running_threads.remove(th)
Removes all threads that return FALSE on isAlive() from the running_threads list 
recipes/Python/578331_Simple_python_thread_manager/recipe-578331.py