text: import logging
  import inspect
  
  from scrapy.spiders import Spider
  from scrapy.utils.misc import  arg_to_iter
  
  
  logger = logging.getLogger(__name__)
  
  
  def iterate_spider_output(result):
      return arg_to_iter(result)
  
  
  def iter_spider_classes(module):
      """Return an iterator over all spider classes defined in the given module
      that can be instantiated (ie. which have name)
      """
      # this needs to be imported here until get rid of the spider manager
      # singleton in scrapy.spider.spiders
      from scrapy.spiders import Spider
  
      for obj in vars(module).values():
          if inspect.isclass(obj) and \
             issubclass(obj, Spider) and \
             obj.__module__ == module.__name__ and \
             getattr(obj, 'name', None):
              yield obj
  
  
  def spidercls_for_request(spider_loader, request, default_spidercls=None,
                            log_none=False, log_multiple=False):
      """Return a spider class that handles the given Request.
  
      This will look for the spiders that can handle the given request (using
      the spider loader) and return a Spider class if (and only if) there is
      only one Spider able to handle the Request.
  
      If multiple spiders (or no spider) are found, it will return the
      default_spidercls passed. It can optionally log if multiple or no spiders
      are found.
      """
      snames = spider_loader.find_by_request(request)
      if len(snames) == 1:
          return spider_loader.load(snames[0])
  
      if len(snames) > 1 and log_multiple:
          logger.error('More than one spider can handle: %(request)s - %(snames)s',
                       {'request': request, 'snames': ', '.join(snames)})
  
      if len(snames) == 0 and log_none:
          logger.error('Unable to find spider that handles: %(request)s',
                       {'request': request})
  
      return default_spidercls
  
  
  class DefaultSpider(Spider):
      name = 'default'
  