#!/usr/bin/env python# -*- coding: utf-8 -*- import urllib2,re,platform#urlib2抓取网页def getContent(url, timeout=5):    content = None    try:        res = urllib2.urlopen(url, timeout=timeout)        content = res.read()    except urllib2.URLError, e:        print e.reason    return content#字符串查找关键词之前内容def getMain(content, keychars=‘#google hosts‘):    pos1 = content.find(keychars)    pos2 = content.find(keychars,pos1+len(keychars))    m = content[pos1:pos2+len(keychars)]    m = m.replace(‘&nbsp;‘,‘ ‘)    r = re.compile(r‘<[\w\s\/]+>‘)    return r.sub("", m)#source host urlurl = ‘http://www.360kb.com/kb/2_122.html‘#标示字符串keychars = ‘#google hosts‘#获取当前操作系统，判断修改文件路径syst = platform.system()if syst==‘Windows‘:    #windows    hosts = ‘C:\\Windows\\System32\\drivers\\etc\\hosts‘else:    #linux    hosts = ‘/etc/hosts‘content = getContent(url, 5)if content==None:    exithostcontents = getMain(content,keychars)fp = open(hosts, ‘rb‘)c = fp.read()fp.close()pos1 = c.find(keychars)if pos1==-1:    result = c+"\n"*2+hostcontentselse :    result = c[:pos1]+"\n"*2+hostcontentsfp = open(hosts, ‘wb‘)fp.write(result)fp.close()