def getRemoteFileSize(url, proxy=None):     """ 通过content-length头获取远程文件大小         url - 目标文件URL         proxy - 代理  """     opener = urllib2.build_opener()     if proxy:         if url.lower().startswith('https://'):             opener.add_handler(urllib2.ProxyHandler({'https' : proxy}))         else:             opener.add_handler(urllib2.ProxyHandler({'http' : proxy}))     try:         request = urllib2.Request(url)         request.get_method = lambda: 'HEAD'         response = opener.open(request)         response.read()     except Exception, e: # 远程文件不存在                return 0     else:         fileSize = dict(response.headers).get('content-length', 0)         return int(fileSize)