python支持多线程的爬虫实例

#!/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()