Scrapy CrawlSpider: how to access item across different levels of parsing

Question

I'm crawling a web site (only two levels deep), and I want to scrape information from sites on both levels. The problem I'm running into, is I want to fill out the fields of one item with information from both levels. How do I do this?

I was thinking having a list of items as an instance variable that will be accessible by all threads (since it's the same instance of the spider), and parse_1 will fill out some fields, and parse_2 will have to check for the correct key before filling out the corresponding value. This method seems burdensome, and I'm still not sure how to make it work.

What I'm thinking is there must be a better way, maybe somehow passing an item to the callback. I don't know how to do that with the Request() method though. Ideas?

Answer 1

From scrapy documentation:

In some cases you may be interested in passing arguments to those callback functions so you can receive the arguments later, in the second callback. You can use the Request.meta attribute for that.

Here’s an example of how to pass an item using this mechanism, to populate different fields from different pages:

def parse_page1(self, response):
    item = MyItem()
    item['main_url'] = response.url
    request = Request("http://www.example.com/some_page.html",
                      callback=self.parse_page2)
    request.meta['item'] = item
    return request

def parse_page2(self, response):
    item = response.meta['item']
    item['other_url'] = response.url
    return item

So, basically you can scrape first page and store all information in item and then send whole item with request for that second level url and have all the information in one item.