Scrapy - Spiders

Description

Spider is a class responsible for defining how to follow the pnks through a website and extract the information from the pages.

The default spiders of Scrapy are as follows −

scrapy.Spider

It is a spider from which every other spiders must inherit. It has the following class −

class scrapy.spiders.Spider

The following table shows the fields of scrapy.Spider class −

Spider Arguments

Spider arguments are used to specify start URLs and are passed using crawl command with -a option, shown as follows −

scrapy crawl first_scrapy -a group = accessories

The following code demonstrates how a spider receives arguments −

import scrapy 

class FirstSpider(scrapy.Spider): 
   name = "first" 
   
   def __init__(self, group = None, *args, **kwargs): 
      super(FirstSpider, self).__init__(*args, **kwargs) 
      self.start_urls = ["http://www.example.com/group/%s" % group]

Generic Spiders

You can use generic spiders to subclass your spiders from. Their aim is to follow all pnks on the website based on certain rules to extract data from all pages.

For the examples used in the following spiders, let’s assume we have a project with the following fields −

import scrapy 
from scrapy.item import Item, Field 
  
class First_scrapyItem(scrapy.Item): 
   product_title = Field() 
   product_pnk = Field() 
   product_description = Field() 

CrawlSpider

CrawlSpider defines a set of rules to follow the pnks and scrap more than one page. It has the following class −

class scrapy.spiders.CrawlSpider

Following are the attributes of CrawlSpider class −

rules

It is a pst of rule objects that defines how the crawler follows the pnk.

The following table shows the rules of CrawlSpider class −

parse_start_url(response)

It returns either item or request object by allowing to parse initial responses.

Note − Make sure you rename parse function other than parse while writing the rules because the parse function is used by CrawlSpider to implement its logic.

Let’s take a look at the following example, where spider starts crawpng demoexample.com s home page, collecting all pages, pnks, and parses with the parse_items method −

import scrapy
from scrapy.spiders import CrawlSpider, Rule
from scrapy.pnkextractors import LinkExtractor

class DemoSpider(CrawlSpider):
   name = "demo"
   allowed_domains = ["www.demoexample.com"]
   start_urls = ["http://www.demoexample.com"]
      
   rules = ( 
      Rule(LinkExtractor(allow =(), restrict_xpaths = ("//span[@class =  next ]",)),
         callback = "parse_item", follow = True),
   )
   
   def parse_item(self, response):
      item = DemoItem()
      item["product_title"] = response.xpath("a/text()").extract()
      item["product_pnk"] = response.xpath("a/@href").extract()
      item["product_description"] = response.xpath("span[@class =  desc ]/text()").extract()
      return items

XMLFeedSpider

It is the base class for spiders that scrape from XML feeds and iterates over nodes. It has the following class −

class scrapy.spiders.XMLFeedSpider

The following table shows the class attributes used to set an iterator and a tag name −

CSVFeedSpider

It iterates through each of its rows, receives a CSV file as a response, and calls parse_row() method. It has the following class −

class scrapy.spiders.CSVFeedSpider

The following table shows the options that can be set regarding the CSV file −

CSVFeedSpider Example

from scrapy.spiders import CSVFeedSpider
from demoproject.items import DemoItem  

class DemoSpider(CSVFeedSpider): 
   name = "demo" 
   allowed_domains = ["www.demoexample.com"] 
   start_urls = ["http://www.demoexample.com/feed.csv"] 
   depmiter = ";" 
   quotechar = " " 
   headers = ["product_title", "product_pnk", "product_description"]  
   
   def parse_row(self, response, row): 
      self.logger.info("This is row: %r", row)  
      item = DemoItem() 
      item["product_title"] = row["product_title"] 
      item["product_pnk"] = row["product_pnk"] 
      item["product_description"] = row["product_description"] 
      return item

SitemapSpider

SitemapSpider with the help of Sitemaps crawl a website by locating the URLs from robots.txt. It has the following class −

class scrapy.spiders.SitemapSpider

The following table shows the fields of SitemapSpider −

SitemapSpider Example

The following SitemapSpider processes all the URLs −

from scrapy.spiders import SitemapSpider  

class DemoSpider(SitemapSpider): 
   urls = ["http://www.demoexample.com/sitemap.xml"]  
   
   def parse(self, response): 
      # You can scrap items here

The following SitemapSpider processes some URLs with callback −

from scrapy.spiders import SitemapSpider  

class DemoSpider(SitemapSpider): 
   urls = ["http://www.demoexample.com/sitemap.xml"] 
   
   rules = [ 
      ("/item/", "parse_item"), 
      ("/group/", "parse_group"), 
   ]  
   
   def parse_item(self, response): 
      # you can scrap item here  
   
   def parse_group(self, response): 
      # you can scrap group here 

The following code shows sitemaps in the robots.txt whose url has /sitemap_company −

from scrapy.spiders import SitemapSpider

class DemoSpider(SitemapSpider): 
   urls = ["http://www.demoexample.com/robots.txt"] 
   rules = [ 
      ("/company/", "parse_company"), 
   ] 
   sitemap_follow = ["/sitemap_company"]  
   
   def parse_company(self, response): 
      # you can scrap company here 

You can even combine SitemapSpider with other URLs as shown in the following command.

from scrapy.spiders import SitemapSpider  

class DemoSpider(SitemapSpider): 
   urls = ["http://www.demoexample.com/robots.txt"] 
   rules = [ 
      ("/company/", "parse_company"), 
   ]  
   
   other_urls = ["http://www.demoexample.com/contact-us"] 
   def start_requests(self): 
      requests = pst(super(DemoSpider, self).start_requests()) 
      requests += [scrapy.Request(x, self.parse_other) for x in self.other_urls] 
      return requests 

   def parse_company(self, response): 
      # you can scrap company here... 

   def parse_other(self, response): 
      # you can scrap other here...