Spiders¶
Spiders are classes which define how a certain site (or a group of sites) will be scraped, including how to perform the crawl (i.e. follow links) and how to extract structured data from their pages (i.e. scraping items). In other words, Spiders are the place where you define the custom behaviour for crawling and parsing pages for a particular site (or, in some cases, a group of sites).
For spiders, the scraping cycle goes through something like this:
You start by generating the initial Requests to crawl the first URLs, and specify a callback function to be called with the response downloaded from those requests.
The first requests to perform are obtained by calling the
start_requests()
method which (by default) generatesRequest
for the URLs specified in thestart_urls
and theparse
method as callback function for the Requests.In the callback function, you parse the response (web page) and return either dicts with extracted data,
Item
objects,Request
objects, or an iterable of these objects. Those Requests will also contain a callback (maybe the same) and will then be downloaded by Scrapy and then their response handled by the specified callback.In callback functions, you parse the page contents, typically using Selectors (but you can also use BeautifulSoup, lxml or whatever mechanism you prefer) and generate items with the parsed data.
Finally, the items returned from the spider will be typically persisted to a database (in some Item Pipeline) or written to a file using Feed exports.
Even though this cycle applies (more or less) to any kind of spider, there are different kinds of default spiders bundled into Scrapy for different purposes. We will talk about those types here.
scrapy.Spider¶
- class scrapy.spiders.Spider¶
This is the simplest spider, and the one from which every other spider must inherit (including spiders that come bundled with Scrapy, as well as spiders that you write yourself). It doesn’t provide any special functionality. It just provides a default
start_requests()
implementation which sends requests from thestart_urls
spider attribute and calls the spider’s methodparse
for each of the resulting responses.- name¶
A string which defines the name for this spider. The spider name is how the spider is located (and instantiated) by Scrapy, so it must be unique. However, nothing prevents you from instantiating more than one instance of the same spider. This is the most important spider attribute and it’s required.
If the spider scrapes a single domain, a common practice is to name the spider after the domain, with or without the TLD. So, for example, a spider that crawls
mywebsite.com
would often be calledmywebsite
.Note
In Python 2 this must be ASCII only.
- allowed_domains¶
An optional list of strings containing domains that this spider is allowed to crawl. Requests for URLs not belonging to the domain names specified in this list (or their subdomains) won’t be followed if
OffsiteMiddleware
is enabled.Let’s say your target url is
https://www.example.com/1.html
, then add'example.com'
to the list.
- start_urls¶
A list of URLs where the spider will begin to crawl from, when no particular URLs are specified. So, the first pages downloaded will be those listed here. The subsequent
Request
will be generated successively from data contained in the start URLs.
- custom_settings¶
A dictionary of settings that will be overridden from the project wide configuration when running this spider. It must be defined as a class attribute since the settings are updated before instantiation.
For a list of available built-in settings see: Built-in settings reference.
- crawler¶
This attribute is set by the
from_crawler()
class method after initializating the class, and links to theCrawler
object to which this spider instance is bound.Crawlers encapsulate a lot of components in the project for their single entry access (such as extensions, middlewares, signals managers, etc). See Crawler API to know more about them.
- settings¶
Configuration for running this spider. This is a
Settings
instance, see the Settings topic for a detailed introduction on this subject.
- logger¶
Python logger created with the Spider’s
name
. You can use it to send log messages through it as described on Logging from Spiders.
- from_crawler(crawler, \*args, \**kwargs)¶
This is the class method used by Scrapy to create your spiders.
You probably won’t need to override this directly because the default implementation acts as a proxy to the
__init__()
method, calling it with the given argumentsargs
and named argumentskwargs
.Nonetheless, this method sets the
crawler
andsettings
attributes in the new instance so they can be accessed later inside the spider’s code.
- start_requests()¶
This method must return an iterable with the first Requests to crawl for this spider. It is called by Scrapy when the spider is opened for scraping. Scrapy calls it only once, so it is safe to implement
start_requests()
as a generator.The default implementation generates
Request(url, dont_filter=True)
for each url instart_urls
.If you want to change the Requests used to start scraping a domain, this is the method to override. For example, if you need to start by logging in using a POST request, you could do:
class MySpider(scrapy.Spider): name = 'myspider' def start_requests(self): return [scrapy.FormRequest("http://www.example.com/login", formdata={'user': 'john', 'pass': 'secret'}, callback=self.logged_in)] def logged_in(self, response): # here you would extract links to follow and return Requests for # each of them, with another callback pass
- parse(response)¶
This is the default callback used by Scrapy to process downloaded responses, when their requests don’t specify a callback.
The
parse
method is in charge of processing the response and returning scraped data and/or more URLs to follow. Other Requests callbacks have the same requirements as theSpider
class.This method, as well as any other Request callback, must return an iterable of
Request
and/or dicts orItem
objects.- Parameters:
response (
Response
) – the response to parse
- log(message[, level, component])¶
Wrapper that sends a log message through the Spider’s
logger
, kept for backward compatibility. For more information see Logging from Spiders.
- closed(reason)¶
Called when the spider closes. This method provides a shortcut to signals.connect() for the
spider_closed
signal.
Let’s see an example:
import scrapy
class MySpider(scrapy.Spider):
name = 'example.com'
allowed_domains = ['example.com']
start_urls = [
'http://www.example.com/1.html',
'http://www.example.com/2.html',
'http://www.example.com/3.html',
]
def parse(self, response):
self.logger.info('A response from %s just arrived!', response.url)
Return multiple Requests and items from a single callback:
import scrapy
class MySpider(scrapy.Spider):
name = 'example.com'
allowed_domains = ['example.com']
start_urls = [
'http://www.example.com/1.html',
'http://www.example.com/2.html',
'http://www.example.com/3.html',
]
def parse(self, response):
for h3 in response.xpath('//h3').getall():
yield {"title": h3}
for href in response.xpath('//a/@href').getall():
yield scrapy.Request(response.urljoin(href), self.parse)
Instead of start_urls
you can use start_requests()
directly;
to give data more structure you can use Items:
import scrapy
from myproject.items import MyItem
class MySpider(scrapy.Spider):
name = 'example.com'
allowed_domains = ['example.com']
def start_requests(self):
yield scrapy.Request('http://www.example.com/1.html', self.parse)
yield scrapy.Request('http://www.example.com/2.html', self.parse)
yield scrapy.Request('http://www.example.com/3.html', self.parse)
def parse(self, response):
for h3 in response.xpath('//h3').getall():
yield MyItem(title=h3)
for href in response.xpath('//a/@href').getall():
yield scrapy.Request(response.urljoin(href), self.parse)
Spider arguments¶
Spiders can receive arguments that modify their behaviour. Some common uses for spider arguments are to define the start URLs or to restrict the crawl to certain sections of the site, but they can be used to configure any functionality of the spider.
Spider arguments are passed through the crawl
command using the
-a
option. For example:
scrapy crawl myspider -a category=electronics
Spiders can access arguments in their __init__ methods:
import scrapy
class MySpider(scrapy.Spider):
name = 'myspider'
def __init__(self, category=None, *args, **kwargs):
super(MySpider, self).__init__(*args, **kwargs)
self.start_urls = ['http://www.example.com/categories/%s' % category]
# ...
The default __init__ method will take any spider arguments and copy them to the spider as attributes. The above example can also be written as follows:
import scrapy
class MySpider(scrapy.Spider):
name = 'myspider'
def start_requests(self):
yield scrapy.Request('http://www.example.com/categories/%s' % self.category)
Keep in mind that spider arguments are only strings.
The spider will not do any parsing on its own.
If you were to set the start_urls
attribute from the command line,
you would have to parse it on your own into a list
using something like
ast.literal_eval
or json.loads
and then set it as an attribute.
Otherwise, you would cause iteration over a start_urls
string
(a very common python pitfall)
resulting in each character being seen as a separate url.
A valid use case is to set the http auth credentials
used by HttpAuthMiddleware
or the user agent
used by UserAgentMiddleware
:
scrapy crawl myspider -a http_user=myuser -a http_pass=mypassword -a user_agent=mybot
Spider arguments can also be passed through the Scrapyd schedule.json
API.
See Scrapyd documentation.
Generic Spiders¶
Scrapy comes with some useful generic spiders that you can use to subclass your spiders from. Their aim is to provide convenient functionality for a few common scraping cases, like following all links on a site based on certain rules, crawling from Sitemaps, or parsing an XML/CSV feed.
For the examples used in the following spiders, we’ll assume you have a project
with a TestItem
declared in a myproject.items
module:
import scrapy
class TestItem(scrapy.Item):
id = scrapy.Field()
name = scrapy.Field()
description = scrapy.Field()
CrawlSpider¶
- class scrapy.spiders.CrawlSpider¶
This is the most commonly used spider for crawling regular websites, as it provides a convenient mechanism for following links by defining a set of rules. It may not be the best suited for your particular web sites or project, but it’s generic enough for several cases, so you can start from it and override it as needed for more custom functionality, or just implement your own spider.
Apart from the attributes inherited from Spider (that you must specify), this class supports a new attribute:
- rules¶
Which is a list of one (or more)
Rule
objects. EachRule
defines a certain behaviour for crawling the site. Rules objects are described below. If multiple rules match the same link, the first one will be used, according to the order they’re defined in this attribute.
This spider also exposes an overrideable method:
Crawling rules¶
- class scrapy.spiders.Rule(link_extractor=None, callback=None, cb_kwargs=None, follow=None, process_links=None, process_request=None)¶
link_extractor
is a Link Extractor object which defines how links will be extracted from each crawled page. Each produced link will be used to generate aRequest
object, which will contain the link’s text in itsmeta
dictionary (under thelink_text
key). If omitted, a default link extractor created with no arguments will be used, resulting in all links being extracted.callback
is a callable or a string (in which case a method from the spider object with that name will be used) to be called for each link extracted with the specified link extractor. This callback receives aResponse
as its first argument and must return either a single instance or an iterable ofItem
,dict
and/orRequest
objects (or any subclass of them). As mentioned above, the receivedResponse
object will contain the text of the link that produced theRequest
in itsmeta
dictionary (under thelink_text
key)Warning
When writing crawl spider rules, avoid using
parse
as callback, since theCrawlSpider
uses theparse
method itself to implement its logic. So if you override theparse
method, the crawl spider will no longer work.cb_kwargs
is a dict containing the keyword arguments to be passed to the callback function.follow
is a boolean which specifies if links should be followed from each response extracted with this rule. Ifcallback
is Nonefollow
defaults toTrue
, otherwise it defaults toFalse
.process_links
is a callable, or a string (in which case a method from the spider object with that name will be used) which will be called for each list of links extracted from each response using the specifiedlink_extractor
. This is mainly used for filtering purposes.process_request
is a callable (or a string, in which case a method from the spider object with that name will be used) which will be called for everyRequest
extracted by this rule. This callable should take said request as first argument and theResponse
from which the request originated as second argument. It must return aRequest
object orNone
(to filter out the request).
CrawlSpider example¶
Let’s now take a look at an example CrawlSpider with rules:
import scrapy
from scrapy.spiders import CrawlSpider, Rule
from scrapy.linkextractors import LinkExtractor
class MySpider(CrawlSpider):
name = 'example.com'
allowed_domains = ['example.com']
start_urls = ['http://www.example.com']
rules = (
# Extract links matching 'category.php' (but not matching 'subsection.php')
# and follow links from them (since no callback means follow=True by default).
Rule(LinkExtractor(allow=('category\.php', ), deny=('subsection\.php', ))),
# Extract links matching 'item.php' and parse them with the spider's method parse_item
Rule(LinkExtractor(allow=('item\.php', )), callback='parse_item'),
)
def parse_item(self, response):
self.logger.info('Hi, this is an item page! %s', response.url)
item = scrapy.Item()
item['id'] = response.xpath('//td[@id="item_id"]/text()').re(r'ID: (\d+)')
item['name'] = response.xpath('//td[@id="item_name"]/text()').get()
item['description'] = response.xpath('//td[@id="item_description"]/text()').get()
item['link_text'] = response.meta['link_text']
return item
This spider would start crawling example.com’s home page, collecting category
links, and item links, parsing the latter with the parse_item
method. For
each item response, some data will be extracted from the HTML using XPath, and
an Item
will be filled with it.
XMLFeedSpider¶
- class scrapy.spiders.XMLFeedSpider¶
XMLFeedSpider is designed for parsing XML feeds by iterating through them by a certain node name. The iterator can be chosen from:
iternodes
,xml
, andhtml
. It’s recommended to use theiternodes
iterator for performance reasons, since thexml
andhtml
iterators generate the whole DOM at once in order to parse it. However, usinghtml
as the iterator may be useful when parsing XML with bad markup.To set the iterator and the tag name, you must define the following class attributes:
- iterator¶
A string which defines the iterator to use. It can be either:
'iternodes'
- a fast iterator based on regular expressions'html'
- an iterator which usesSelector
. Keep in mind this uses DOM parsing and must load all DOM in memory which could be a problem for big feeds'xml'
- an iterator which usesSelector
. Keep in mind this uses DOM parsing and must load all DOM in memory which could be a problem for big feeds
It defaults to:
'iternodes'
.
- itertag¶
A string with the name of the node (or element) to iterate in. Example:
itertag = 'product'
- namespaces¶
A list of
(prefix, uri)
tuples which define the namespaces available in that document that will be processed with this spider. Theprefix
anduri
will be used to automatically register namespaces using theregister_namespace()
method.You can then specify nodes with namespaces in the
itertag
attribute.Example:
class YourSpider(XMLFeedSpider): namespaces = [('n', 'http://www.sitemaps.org/schemas/sitemap/0.9')] itertag = 'n:url' # ...
Apart from these new attributes, this spider has the following overrideable methods too:
- adapt_response(response)¶
A method that receives the response as soon as it arrives from the spider middleware, before the spider starts parsing it. It can be used to modify the response body before parsing it. This method receives a response and also returns a response (it could be the same or another one).
- parse_node(response, selector)¶
This method is called for the nodes matching the provided tag name (
itertag
). Receives the response and anSelector
for each node. Overriding this method is mandatory. Otherwise, you spider won’t work. This method must return either aItem
object, aRequest
object, or an iterable containing any of them.
- process_results(response, results)¶
This method is called for each result (item or request) returned by the spider, and it’s intended to perform any last time processing required before returning the results to the framework core, for example setting the item IDs. It receives a list of results and the response which originated those results. It must return a list of results (Items or Requests).
XMLFeedSpider example¶
These spiders are pretty easy to use, let’s have a look at one example:
from scrapy.spiders import XMLFeedSpider
from myproject.items import TestItem
class MySpider(XMLFeedSpider):
name = 'example.com'
allowed_domains = ['example.com']
start_urls = ['http://www.example.com/feed.xml']
iterator = 'iternodes' # This is actually unnecessary, since it's the default value
itertag = 'item'
def parse_node(self, response, node):
self.logger.info('Hi, this is a <%s> node!: %s', self.itertag, ''.join(node.getall()))
item = TestItem()
item['id'] = node.xpath('@id').get()
item['name'] = node.xpath('name').get()
item['description'] = node.xpath('description').get()
return item
Basically what we did up there was to create a spider that downloads a feed from
the given start_urls
, and then iterates through each of its item
tags,
prints them out, and stores some random data in an Item
.
CSVFeedSpider¶
- class scrapy.spiders.CSVFeedSpider¶
This spider is very similar to the XMLFeedSpider, except that it iterates over rows, instead of nodes. The method that gets called in each iteration is
parse_row()
.- delimiter¶
A string with the separator character for each field in the CSV file Defaults to
','
(comma).
- quotechar¶
A string with the enclosure character for each field in the CSV file Defaults to
'"'
(quotation mark).
- headers¶
A list of the column names in the CSV file.
- parse_row(response, row)¶
Receives a response and a dict (representing each row) with a key for each provided (or detected) header of the CSV file. This spider also gives the opportunity to override
adapt_response
andprocess_results
methods for pre- and post-processing purposes.
CSVFeedSpider example¶
Let’s see an example similar to the previous one, but using a
CSVFeedSpider
:
from scrapy.spiders import CSVFeedSpider
from myproject.items import TestItem
class MySpider(CSVFeedSpider):
name = 'example.com'
allowed_domains = ['example.com']
start_urls = ['http://www.example.com/feed.csv']
delimiter = ';'
quotechar = "'"
headers = ['id', 'name', 'description']
def parse_row(self, response, row):
self.logger.info('Hi, this is a row!: %r', row)
item = TestItem()
item['id'] = row['id']
item['name'] = row['name']
item['description'] = row['description']
return item
SitemapSpider¶
- class scrapy.spiders.SitemapSpider¶
SitemapSpider allows you to crawl a site by discovering the URLs using Sitemaps.
It supports nested sitemaps and discovering sitemap urls from robots.txt.
- sitemap_urls¶
A list of urls pointing to the sitemaps whose urls you want to crawl.
You can also point to a robots.txt and it will be parsed to extract sitemap urls from it.
- sitemap_rules¶
A list of tuples
(regex, callback)
where:regex
is a regular expression to match urls extracted from sitemaps.regex
can be either a str or a compiled regex object.callback is the callback to use for processing the urls that match the regular expression.
callback
can be a string (indicating the name of a spider method) or a callable.
For example:
sitemap_rules = [('/product/', 'parse_product')]
Rules are applied in order, and only the first one that matches will be used.
If you omit this attribute, all urls found in sitemaps will be processed with the
parse
callback.
- sitemap_follow¶
A list of regexes of sitemap that should be followed. This is only for sites that use Sitemap index files that point to other sitemap files.
By default, all sitemaps are followed.
- sitemap_alternate_links¶
Specifies if alternate links for one
url
should be followed. These are links for the same website in another language passed within the sameurl
block.For example:
<url> <loc>http://example.com/</loc> <xhtml:link rel="alternate" hreflang="de" href="http://example.com/de"/> </url>
With
sitemap_alternate_links
set, this would retrieve both URLs. Withsitemap_alternate_links
disabled, onlyhttp://example.com/
would be retrieved.Default is
sitemap_alternate_links
disabled.
- sitemap_filter(entries)¶
This is a filter function that could be overridden to select sitemap entries based on their attributes.
For example:
<url> <loc>http://example.com/</loc> <lastmod>2005-01-01</lastmod> </url>
We can define a
sitemap_filter
function to filterentries
by date:from datetime import datetime from scrapy.spiders import SitemapSpider class FilteredSitemapSpider(SitemapSpider): name = 'filtered_sitemap_spider' allowed_domains = ['example.com'] sitemap_urls = ['http://example.com/sitemap.xml'] def sitemap_filter(self, entries): for entry in entries: date_time = datetime.strptime(entry['lastmod'], '%Y-%m-%d') if date_time.year >= 2005: yield entry
This would retrieve only
entries
modified on 2005 and the following years.Entries are dict objects extracted from the sitemap document. Usually, the key is the tag name and the value is the text inside it.
It’s important to notice that:
as the loc attribute is required, entries without this tag are discarded
alternate links are stored in a list with the key
alternate
(seesitemap_alternate_links
)namespaces are removed, so lxml tags named as
{namespace}tagname
become onlytagname
If you omit this method, all entries found in sitemaps will be processed, observing other attributes and their settings.
SitemapSpider examples¶
Simplest example: process all urls discovered through sitemaps using the
parse
callback:
from scrapy.spiders import SitemapSpider
class MySpider(SitemapSpider):
sitemap_urls = ['http://www.example.com/sitemap.xml']
def parse(self, response):
pass # ... scrape item here ...
Process some urls with certain callback and other urls with a different callback:
from scrapy.spiders import SitemapSpider
class MySpider(SitemapSpider):
sitemap_urls = ['http://www.example.com/sitemap.xml']
sitemap_rules = [
('/product/', 'parse_product'),
('/category/', 'parse_category'),
]
def parse_product(self, response):
pass # ... scrape product ...
def parse_category(self, response):
pass # ... scrape category ...
Follow sitemaps defined in the robots.txt file and only follow sitemaps
whose url contains /sitemap_shop
:
from scrapy.spiders import SitemapSpider
class MySpider(SitemapSpider):
sitemap_urls = ['http://www.example.com/robots.txt']
sitemap_rules = [
('/shop/', 'parse_shop'),
]
sitemap_follow = ['/sitemap_shops']
def parse_shop(self, response):
pass # ... scrape shop here ...
Combine SitemapSpider with other sources of urls:
from scrapy.spiders import SitemapSpider
class MySpider(SitemapSpider):
sitemap_urls = ['http://www.example.com/robots.txt']
sitemap_rules = [
('/shop/', 'parse_shop'),
]
other_urls = ['http://www.example.com/about']
def start_requests(self):
requests = list(super(MySpider, self).start_requests())
requests += [scrapy.Request(x, self.parse_other) for x in self.other_urls]
return requests
def parse_shop(self, response):
pass # ... scrape shop here ...
def parse_other(self, response):
pass # ... scrape other here ...