python线程优先级队列是什么？

# !/usr/bin/python# -*- coding: UTF-8 -*-import Queueimport threadingimport timeexitFlag = 0class myThread(threading.Thread):   def __init__(self, threadID, name, q):      threading.Thread.__init__(self)      self.threadID = threadID      self.name = name      self.q = q   def run(self):      print "Starting " + self.name      process_data(self.name, self.q)      print "Exiting " + self.namedef process_data(threadName, q):   while not exitFlag:      queueLock.acquire()      if not workQueue.empty():         data = q.get()         queueLock.release()         print "%s processing %s" % (threadName, data)      else:         queueLock.release()      time.sleep(1)threadList = ["Thread-1", "Thread-2", "Thread-3"]nameList = ["One", "Two", "Three", "Four", "Five"]queueLock = threading.Lock()workQueue = Queue.Queue(10)threads = []threadID = 1# 创建新线程for tName in threadList:   thread = myThread(threadID, tName, workQueue)   thread.start()   threads.append(thread)   threadID += 1# 填充队列queueLock.acquire()for word in nameList:   workQueue.put(word)queueLock.release()# 等待队列清空while not workQueue.empty():   pass# 通知线程是时候退出exitFlag = 1# 等待所有线程完成for t in threads:   t.join()print "Exiting Main Thread"

Starting Thread-1Starting Thread-2Starting Thread-3Thread-1 processing OneThread-2 processing TwoThread-3 processing ThreeThread-1 processing FourThread-2 processing FiveExiting Thread-3Exiting Thread-1Exiting Thread-2Exiting Main Thread