本文實(shí)例講述了Python多線程原理與用法。分享給大家供大家參考，具體如下：

先來看個栗子：

下面來看一下I/O秘籍型的線程，舉個栗子——爬蟲，下面是爬下來的圖片用4個線程去寫文件

#!/usr/bin/env python# -*- coding:utf-8 -*-import reimport urllibimport threadingimport Queueimport timeitdef getHtml(url):  html_page = urllib.urlopen(url).read()  return html_page# 提取網(wǎng)頁中圖片的URLdef getUrl(html):  pattern = r'src="(http://img.*?)"' # 正則表達(dá)式  imgre = re.compile(pattern)  imglist = re.findall(imgre, html) # re.findall(pattern,string) 在string中尋找所有匹配成功的字符串，以列表形式返回值  return imglistclass getImg(threading.Thread):  def __init__(self, queue, thread_name=0): # 線程公用一個隊(duì)列    threading.Thread.__init__(self)    self.queue = queue    self.thread_name = thread_name    self.start() # 啟動線程  # 使用隊(duì)列實(shí)現(xiàn)進(jìn)程間通信  def run(self):    global count    while (True):      imgurl = self.queue.get() # 調(diào)用隊(duì)列對象的get()方法從隊(duì)頭刪除并返回一個項(xiàng)目      urllib.urlretrieve(imgurl, 'E:/mnt/girls/%s.jpg' % count)      count += 1      if self.queue.empty():        break      self.queue.task_done() # 當(dāng)使用者線程調(diào)用 task_done() 以表示檢索了該項(xiàng)目、并完成了所有的工作時，那么未完成的任務(wù)的總數(shù)就會減少。imglist = []def main():  global imglist  url = "http://huaban.com/favorite/beauty/" # 要爬的網(wǎng)頁地址  html = getHtml(url)  imglist = getUrl(html)def main_1():  global count  threads = []  count = 0  queue = Queue.Queue()  # 將所有任務(wù)加入隊(duì)列  for img in imglist:    queue.put(img)  # 多線程爬去圖片  for i in range(4):    thread = getImg(queue, i)    threads.append(thread)  # 阻塞線程，直到線程執(zhí)行完成  for thread in threads:    thread.join()if __name__ == '__main__':  main()  t = timeit.Timer(main_1)  print t.timeit(1)

4個線程的執(zhí)行耗時為：0.421320716723秒

修改一下main_1換成單線程的：

def main_1():  global count  threads = []  count = 0  queue = Queue.Queue()  # 將所有任務(wù)加入隊(duì)列  for img in imglist:    queue.put(img)  # 多線程爬去圖片  for i in range(1):    thread = getImg(queue, i)    threads.append(thread)  # 阻塞線程，直到線程執(zhí)行完成  for thread in threads:    thread.join()

單線程的執(zhí)行耗時為：1.35626623274秒

再來看一個：

#!/usr/bin/env python# -*- coding:utf-8 -*-import threadingimport timeitdef countdown(n):  while n > 0:    n -= 1def task1():  COUNT = 100000000  thread1 = threading.Thread(target=countdown, args=(COUNT,))  thread1.start()  thread1.join()def task2():  COUNT = 100000000  thread1 = threading.Thread(target=countdown, args=(COUNT // 2,))  thread2 = threading.Thread(target=countdown, args=(COUNT // 2,))  thread1.start()  thread2.start()  thread1.join()  thread2.join()if __name__ == '__main__':  t1 = timeit.Timer(task1)  print "countdown in one thread ", t1.timeit(1)  t2 = timeit.Timer(task2)  print "countdown in two thread ", t2.timeit(1)