global total

    try:
        html = etree.HTML(item)
        result = html.xpath('//div[contains(@id,"qiushi_tag")]')
        for site in result:
            try:
                imgUrl = site.xpath('.//img/@src')[0]
                title = site.xpath('.//h2')[0].text
                content = site.xpath('.//div[@class="content"]/span')[0].text.strip()
                vote = None
                comments = None
                try:
                    vote = site.xpath('.//i')[0].text
                    comments = site.xpath('.//i')[1].text
                except:
                    pass
                result = {
                    'imgUrl': imgUrl,
                    'title': title,
                    'content': content,
                    'vote': vote,
                    'comments': comments,
                }

                with self.lock:
                    # print 'write %s' % json.dumps(result)
                    self.f.write(json.dumps(result, ensure_ascii=False).encode('utf-8') + "\n")

            except Exception, e:
                print 'site in result', e
    except Exception, e:
        print 'parse_data', e
    with self.lock:
        total += 1
        
        

这里用了两次的with lock 第一个是加锁，防止竞争写资源，但是第二个为啥又是with lock 这两个啥关系？