code: def is_usable(host, port, timeout=3):
      
      try:
          proxies = {
              'http': 'http://%s:%s' % (host, port),
              'https': 'https://%s:%s' % (host, port)
          }
          requests.get('http://www.baidu.com/', proxies=proxies, timeout=timeout)
      except HTTPError:
          print('failed: ', host, port)
          return False
      else:
          print('success: ', host, port)
          return True
docs: 测试代理是否可用
  
      params
      ----------
      host        ip地址
      port        端口号
      timeout     默认值为3，通过设置这个参数可以过滤掉一些速度慢的代理
  
      example
      ----------
      is_usable('222.180.24.13', '808', timeout=3)