Question

Suppose this is my code

from scrapy.spider import BaseSpider
from scrapy.selector import HtmlXPathSelector

from dmoz.items import DmozItem

class DmozSpider(BaseSpider):
   domain_name = "dmoz.org"
   start_urls = [
       "http://www.dmoz.org/Computers/Programming/Languages/Python/Books/",
       "http://www.dmoz.org/Computers/Programming/Languages/Python/Resources/"
   ]

   def parse(self, response):
       hxs = HtmlXPathSelector(response)
       sites = hxs.select('//ul[2]/li')
       items = []
       for site in sites:
           item = DmozItem()
           item['title'] = site.select('a/text()').extract()
           item['link'] = site.select('a/@href').extract()
           item['desc'] = site.select('text()').extract()
           items.append(item)
       return items

SPIDER = DmozSpider()

If i have used crawlSpider then i could uses Rules to implement thelink extractor but how can i mention rules in base spider. Like in above example. Because rules is only avaialble in crawlspider not base spider

Answer 1

Perhaps you could parse the response for your rule criteria and then pass the successful responses on to a second callback? Pseudo-code below:

def parse(self, response):
    # check response for rule criteria
    ...
    if rule: 
        # create new request to pass to second callback
        req = Request("http://www.example.com/follow", callback=self.parse2)
        return req

def parse2(self, response):
    hxs = HtmlXPathSelector(response)
    # do stuff with the successful response