Python多线程爬虫简单示例-Python Tutorial-php.cn

python是支持多线程的，主要是通过thread和threading这两个模块来实现的。thread模块是比较底层的模块，threading模块是对thread做了一些包装的，可以更加方便的使用。

虽然python的多线程受GIL限制，并不是真正的多线程，但是对于I/O密集型计算还是能明显提高效率，比如说爬虫。

下面用一个实例来验证多线程的效率。代码只涉及页面获取，并没有解析出来。

# -*-coding:utf-8 -*-
import urllib2, time
import threading
 
 
class MyThread(threading.Thread):
  def __init__(self, func, args):
    threading.Thread.__init__(self)
    self.args = args
    self.func = func
 
  def run(self):
    apply(self.func, self.args)
 
 
def open_url(url):
  request = urllib2.Request(url)
  html = urllib2.urlopen(request).read()
  print len(html)
  return html
 
if __name__ == '__main__':
  # 构造url列表
  urlList = []
  for p in range(1, 10):
    urlList.append('http://s.wanfangdata.com.cn/Paper.aspx&#63;q=%E5%8C%BB%E5%AD%A6&p=' + str(p))
   
  # 一般方式
  n_start = time.time()
  for each in urlList:
    open_url(each)
  n_end = time.time()
  print 'the normal way take %s s' % (n_end-n_start)
   
  # 多线程
  t_start = time.time()
  threadList = [MyThread(open_url, (url,)) for url in urlList]
  for t in threadList:
    t.setDaemon(True)
    t.start()
  for i in threadList:
    i.join()
  t_end = time.time()
  print 'the thread way take %s s' % (t_end-t_start)

Copy after login

分别用两种方式获取10个访问速度比较慢的网页，一般方式耗时50s，多线程耗时10s。

多线程代码解读:

# 创建线程类，继承Thread类
class MyThread(threading.Thread):
  def __init__(self, func, args):
    threading.Thread.__init__(self) # 调用父类的构造函数
    self.args = args
    self.func = func
 
  def run(self): # 线程活动方法
    apply(self.func, self.args)

Copy after login

threadList = [MyThread(open_url, (url,)) for url in urlList] # 调用线程类创建新线程，返回线程列表
  for t in threadList:
    t.setDaemon(True) # 设置守护线程，父线程会等待子线程执行完后再退出
    t.start() # 线程开启
  for i in threadList:
    i.join() # 等待线程终止，等子线程执行完后再执行父线程

Copy after login

以上就是本文的全部内容，希望对大家的学习有所帮助。

Related labels：

python Multithreading reptile

source：php.cn

Previous article：两个命令把 Vim 打造成 Python IDE的方法 Next article：python迭代器与生成器详解

Statement of this Website

The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn