Que fait if __name__ == "__main__" ?

Que se passe-t-il lors de l'appel de if __name__ == "__main__": ?

# Threading examplenimport time, threadnndef myfunction(string, sleeptime, lock, *args):n    while 1:n        lock.acquire()n        time.sleep(sleeptime)n        lock.release()n        time.sleep(sleeptime)nif __name__ == "__main__":n    lock = thread.allocate_lock()n    threa