国产高清在线不卡,麻豆播放,国产福利写真视频在线观看

本文實例講述了Python自定義scrapy中間模塊避免重復采集的方法。分享給大家供大家參考。具體如下：

				?

									from scrapy import log

									from scrapy.http import Request

									from scrapy.item import BaseItem

									from scrapy.utils.request import request_fingerprint

									from myproject.items import MyItem

									class IgnoreVisitedItems(object):

									  """Middleware to ignore re-visiting item pages if they

									  were already visited before. 

									  The requests to be filtered by have a meta['filter_visited']

									  flag enabled and optionally define an id to use 

									  for identifying them, which defaults the request fingerprint,

									  although you'd want to use the item id,

									  if you already have it beforehand to make it more robust.

									  """

									  FILTER_VISITED = 'filter_visited'

									  VISITED_ID = 'visited_id'

									  CONTEXT_KEY = 'visited_ids'

									  def process_spider_output(self, response, result, spider):

									    context = getattr(spider, 'context', {})

									    visited_ids = context.setdefault(self.CONTEXT_KEY, {})

									    ret = []

									    for x in result:

									      visited = False

									      if isinstance(x, Request):

									        if self.FILTER_VISITED in x.meta:

									          visit_id = self._visited_id(x)

									          if visit_id in visited_ids:

									            log.msg("Ignoring already visited: %s" % x.url,

									                level=log.INFO, spider=spider)

									            visited = True

									      elif isinstance(x, BaseItem):

									        visit_id = self._visited_id(response.request)

									        if visit_id:

									          visited_ids[visit_id] = True

									          x['visit_id'] = visit_id

									          x['visit_status'] = 'new'

									      if visited:

									        ret.append(MyItem(visit_id=visit_id, visit_status='old'))

									      else:

									        ret.append(x)

									    return ret

									  def _visited_id(self, request):

									    return request.meta.get(self.VISITED_ID) or request_fingerprint(request)