基python实现多线程网页爬虫

#!/usr/bin/env python
#coding=utf-8
import threading
import urllib
import re
import time
g_mutex=threading.Condition()
g_pages=[] #从中解析所有url链接
g_queueURL=[] #等待爬取的url链接列表
g_existURL=[] #已经爬取过的url链接列表
g_failedURL=[] #下载失败的url链接列表
g_totalcount=0 #下载过的页面数
class Crawler:
  def __init__(self,crawlername,url,threadnum):
    self.crawlername=crawlername
    self.url=url
    self.threadnum=threadnum
    self.threadpool=[]
    self.logfile=file("log.txt",'w')
  def craw(self):
    global g_queueURL
    g_queueURL.append(url)  
    depth=0
    print self.crawlername+" 启动..."
    while(len(g_queueURL)!=0):
      depth+=1
      print 'Searching depth ',depth,'...\n\n'
      self.logfile.write("URL:"+g_queueURL[0]+"........")
      self.downloadAll()
      self.updateQueueURL()
      content='\n>>>Depth '+str(depth)+':\n'
      self.logfile.write(content)
      i=0
      while i<len(g_queueURL):
        content=str(g_totalcount+i)+'->'+g_queueURL[i]+'\n'
        self.logfile.write(content)
        i+=1
  def downloadAll(self):
    global g_queueURL
    global g_totalcount
    i=0
    while i<len(g_queueURL):
      j=0
      while j<self.threadnum and i+j < len(g_queueURL):
        g_totalcount+=1
        threadresult=self.download(g_queueURL[i+j],str(g_totalcount)+'.html',j)
        if threadresult!=None:
          print 'Thread started:',i+j,'--File number =',g_totalcount
        j+=1
      i+=j
      for thread in self.threadpool:
        thread.join(30)
      threadpool=[]
    g_queueURL=[]
  def download(self,url,filename,tid):
    crawthread=CrawlerThread(url,filename,tid)
    self.threadpool.append(crawthread)
    crawthread.start()
  def updateQueueURL(self):
    global g_queueURL
    global g_existURL
    newUrlList=[]
    for content in g_pages:
      newUrlList+=self.getUrl(content)
    g_queueURL=list(set(newUrlList)-set(g_existURL))  
  def getUrl(self,content):
    reg=r'"(http://.+?)"'
    regob=re.compile(reg,re.DOTALL)
    urllist=regob.findall(content)
    return urllist
class CrawlerThread(threading.Thread):
  def __init__(self,url,filename,tid):
    threading.Thread.__init__(self)
    self.url=url
    self.filename=filename
    self.tid=tid
  def run(self):
    global g_mutex
    global g_failedURL
    global g_queueURL
    try:
      page=urllib.urlopen(self.url)
      html=page.read()
      fout=file(self.filename,'w')
      fout.write(html)
      fout.close()
    except Exception,e:
      g_mutex.acquire()
      g_existURL.append(self.url)
      g_failedURL.append(self.url)
      g_mutex.release()
      print 'Failed downloading and saving',self.url
      print e
      return None
    g_mutex.acquire()
    g_pages.append(html)
    g_existURL.append(self.url)
    g_mutex.release()
if __name__=="__main__":
  url=raw_input("请输入url入口:\n")
  threadnum=int(raw_input("设置线程数:"))
  crawlername="小小爬虫"
  crawler=Crawler(crawlername,url,threadnum)
  crawler.craw()