.. _topics-spiders:

=======
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:

1. 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
   :meth:`~scrapy.Spider.start_requests` method which (by default)
   generates :class:`~scrapy.Request` for the URLs specified in the
   :attr:`~scrapy.Spider.start_urls` and the
   :attr:`~scrapy.Spider.parse` method as callback function for the
   Requests.

2. In the callback function, you parse the response (web page) and return
   :ref:`item objects <topics-items>`,
   :class:`~scrapy.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.

3. In callback functions, you parse the page contents, typically using
   :ref:`topics-selectors` (but you can also use BeautifulSoup, lxml or whatever
   mechanism you prefer) and generate items with the parsed data.

4. Finally, the items returned from the spider will be typically persisted to a
   database (in some :ref:`Item Pipeline <topics-item-pipeline>`) or written to
   a file using :ref:`topics-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.

.. _topics-spiders-ref:

scrapy.Spider
=============

.. class:: scrapy.spiders.Spider
.. class:: scrapy.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 :meth:`start_requests` implementation which sends requests from
   the :attr:`start_urls` spider attribute and calls the spider's method ``parse``
   for each of the resulting responses.

   .. attribute:: 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 called
       ``mywebsite``.

   .. attribute:: 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
       :class:`~scrapy.spidermiddlewares.offsite.OffsiteMiddleware` is enabled.

       Let's say your target url is ``https://www.example.com/1.html``,
       then add ``'example.com'`` to the list.

   .. attribute:: 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 :class:`~scrapy.Request` will be generated successively from data
       contained in the start URLs.

   .. attribute:: 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:
      :ref:`topics-settings-ref`.

   .. attribute:: crawler

      This attribute is set by the :meth:`from_crawler` class method after
      initializing the class, and links to the
      :class:`~scrapy.crawler.Crawler` 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 :ref:`topics-api-crawler` to know more about them.

   .. attribute:: settings

      Configuration for running this spider. This is a
      :class:`~scrapy.settings.Settings` instance, see the
      :ref:`topics-settings` topic for a detailed introduction on this subject.

   .. attribute:: logger

      Python logger created with the Spider's :attr:`name`. You can use it to
      send log messages through it as described on
      :ref:`topics-logging-from-spiders`.

   .. attribute:: state

      A dict you can use to persist some spider state between batches.
      See :ref:`topics-keeping-persistent-state-between-batches` to know more about it.

   .. method:: 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 :meth:`__init__` method, calling
       it with the given arguments ``args`` and named arguments ``kwargs``.

       Nonetheless, this method sets the :attr:`crawler` and :attr:`settings`
       attributes in the new instance so they can be accessed later inside the
       spider's code.

       .. versionchanged:: 2.11

           The settings in ``crawler.settings`` can now be modified in this
           method, which is handy if you want to modify them based on
           arguments. As a consequence, these settings aren't the final values
           as they can be modified later by e.g. :ref:`add-ons
           <topics-addons>`. For the same reason, most of the
           :class:`~scrapy.crawler.Crawler` attributes aren't initialized at
           this point.

           The final settings and the initialized
           :class:`~scrapy.crawler.Crawler` attributes are available in the
           :meth:`start_requests` method, handlers of the
           :signal:`engine_started` signal and later.

       :param crawler: crawler to which the spider will be bound
       :type crawler: :class:`~scrapy.crawler.Crawler` instance

       :param args: arguments passed to the :meth:`__init__` method
       :type args: list

       :param kwargs: keyword arguments passed to the :meth:`__init__` method
       :type kwargs: dict

   .. classmethod:: update_settings(settings)

       The ``update_settings()`` method is used to modify the spider's settings
       and is called during initialization of a spider instance.

       It takes a :class:`~scrapy.settings.Settings` object as a parameter and
       can add or update the spider's configuration values. This method is a
       class method, meaning that it is called on the :class:`~scrapy.Spider`
       class and allows all instances of the spider to share the same
       configuration.

       While per-spider settings can be set in
       :attr:`~scrapy.Spider.custom_settings`, using ``update_settings()``
       allows you to dynamically add, remove or change settings based on other
       settings, spider attributes or other factors and use setting priorities
       other than ``'spider'``. Also, it's easy to extend ``update_settings()``
       in a subclass by overriding it, while doing the same with
       :attr:`~scrapy.Spider.custom_settings` can be hard.

       For example, suppose a spider needs to modify :setting:`FEEDS`:

       .. code-block:: python

           import scrapy


           class MySpider(scrapy.Spider):
               name = "myspider"
               custom_feed = {
                   "/home/user/documents/items.json": {
                       "format": "json",
                       "indent": 4,
                   }
               }

               @classmethod
               def update_settings(cls, settings):
                   super().update_settings(settings)
                   settings.setdefault("FEEDS", {}).update(cls.custom_feed)

   .. method:: 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
       :meth:`start_requests` as a generator.

       The default implementation generates ``Request(url, dont_filter=True)``
       for each url in :attr:`start_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:

       .. code-block:: python

           import scrapy


           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

   .. method:: 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 the :class:`Spider` class.

       This method, as well as any other Request callback, must return a
       :class:`~scrapy.Request` object, an :ref:`item object <topics-items>`, an
       iterable of :class:`~scrapy.Request` objects and/or :ref:`item objects
       <topics-items>`, or ``None``.

       :param response: the response to parse
       :type response: :class:`~scrapy.http.Response`

   .. method:: log(message, [level, component])

       Wrapper that sends a log message through the Spider's :attr:`logger`,
       kept for backward compatibility. For more information see
       :ref:`topics-logging-from-spiders`.

   .. method:: closed(reason)

       Called when the spider closes. This method provides a shortcut to
       signals.connect() for the :signal:`spider_closed` signal.

Let's see an example:

.. code-block:: python

    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:

.. code-block:: python

    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 :attr:`~.start_urls` you can use :meth:`~.start_requests` directly;
to give data more structure you can use :class:`~scrapy.Item` objects:

.. skip: next
.. code-block:: python

    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)

.. _spiderargs:

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 :command:`crawl` command using the
``-a`` option. For example::

    scrapy crawl myspider -a category=electronics

Spiders can access arguments in their `__init__` methods:

.. code-block:: python

    import scrapy


    class MySpider(scrapy.Spider):
        name = "myspider"

        def __init__(self, category=None, *args, **kwargs):
            super(MySpider, self).__init__(*args, **kwargs)
            self.start_urls = [f"http://www.example.com/categories/{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:

.. code-block:: python

    import scrapy


    class MySpider(scrapy.Spider):
        name = "myspider"

        def start_requests(self):
            yield scrapy.Request(f"http://www.example.com/categories/{self.category}")

If you are :ref:`running Scrapy from a script <run-from-script>`, you can 
specify spider arguments when calling 
:class:`CrawlerProcess.crawl <scrapy.crawler.CrawlerProcess.crawl>` or
:class:`CrawlerRunner.crawl <scrapy.crawler.CrawlerRunner.crawl>`:

.. skip: next
.. code-block:: python

    process = CrawlerProcess()
    process.crawl(MySpider, category="electronics")

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 :func:`ast.literal_eval` or :func:`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 :class:`~scrapy.downloadermiddlewares.httpauth.HttpAuthMiddleware`
or the user agent
used by :class:`~scrapy.downloadermiddlewares.useragent.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`_.

.. _builtin-spiders:

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:

.. code-block:: python

    import scrapy


    class TestItem(scrapy.Item):
        id = scrapy.Field()
        name = scrapy.Field()
        description = scrapy.Field()


.. currentmodule:: scrapy.spiders

CrawlSpider
-----------

.. class:: 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:

   .. attribute:: rules

       Which is a list of one (or more) :class:`Rule` objects.  Each :class:`Rule`
       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 overridable method:

   .. method:: parse_start_url(response, **kwargs)

      This method is called for each response produced for the URLs in
      the spider's ``start_urls`` attribute. It allows to parse
      the initial responses and must return either an
      :ref:`item object <topics-items>`, a :class:`~scrapy.Request`
      object, or an iterable containing any of them.

Crawling rules
~~~~~~~~~~~~~~

.. autoclass:: Rule

   ``link_extractor`` is a :ref:`Link Extractor <topics-link-extractors>` object which
   defines how links will be extracted from each crawled page. Each produced link will
   be used to generate a :class:`~scrapy.Request` object, which will contain the
   link's text in its ``meta`` dictionary (under the ``link_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 a :class:`~scrapy.http.Response`
   as its first argument and must return either a single instance or an iterable of
   :ref:`item objects <topics-items>` and/or :class:`~scrapy.Request` objects
   (or any subclass of them). As mentioned above, the received :class:`~scrapy.http.Response`
   object will contain the text of the link that produced the :class:`~scrapy.Request`
   in its ``meta`` dictionary (under the ``link_text`` key)

   ``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. If ``callback`` is None ``follow`` defaults
   to ``True``, otherwise it defaults to ``False``.

   ``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 specified ``link_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 every
   :class:`~scrapy.Request` extracted by this rule. This callable should
   take said request as first argument and the :class:`~scrapy.http.Response`
   from which the request originated as second argument. It must return a
   ``Request`` object or ``None`` (to filter out the request).

   ``errback`` is a callable or a string (in which case a method from the spider
   object with that name will be used) to be called if any exception is
   raised while processing a request generated by the rule.
   It receives a :class:`Twisted Failure <twisted.python.failure.Failure>`
   instance as first parameter.

   .. warning:: Because of its internal implementation, you must explicitly set
      callbacks for new requests when writing :class:`CrawlSpider`-based spiders;
      unexpected behaviour can occur otherwise.

   .. versionadded:: 2.0
      The *errback* parameter.

CrawlSpider example
~~~~~~~~~~~~~~~~~~~

Let's now take a look at an example CrawlSpider with rules:

.. code-block:: python

    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=(r"category\.php",), deny=(r"subsection\.php",))),
            # Extract links matching 'item.php' and parse them with the spider's method parse_item
            Rule(LinkExtractor(allow=(r"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"]
            url = response.xpath('//td[@id="additional_data"]/@href').get()
            return response.follow(
                url, self.parse_additional_page, cb_kwargs=dict(item=item)
            )

        def parse_additional_page(self, response, item):
            item["additional_data"] = response.xpath(
                '//p[@id="additional_data"]/text()'
            ).get()
            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 :class:`~scrapy.Item` will be filled with it.

XMLFeedSpider
-------------

.. class:: 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``,
    and ``html``.  It's recommended to use the ``iternodes`` iterator for
    performance reasons, since the ``xml`` and ``html`` iterators generate the
    whole DOM at once in order to parse it.  However, using ``html`` 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:

    .. attribute:: 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 uses :class:`~scrapy.Selector`.
             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 uses :class:`~scrapy.Selector`.
             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'``.

    .. attribute:: itertag

        A string with the name of the node (or element) to iterate in. Example::

            itertag = 'product'

    .. attribute:: namespaces

        A list of ``(prefix, uri)`` tuples which define the namespaces
        available in that document that will be processed with this spider. The
        ``prefix`` and ``uri`` will be used to automatically register
        namespaces using the
        :meth:`~scrapy.Selector.register_namespace` method.

        You can then specify nodes with namespaces in the :attr:`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 overridable
    methods too:

    .. method:: 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).

    .. method:: parse_node(response, selector)

        This method is called for the nodes matching the provided tag name
        (``itertag``).  Receives the response and an
        :class:`~scrapy.Selector` for each node.  Overriding this
        method is mandatory. Otherwise, you spider won't work.  This method
        must return an :ref:`item object <topics-items>`, a
        :class:`~scrapy.Request` object, or an iterable containing any of
        them.

    .. method:: 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).

    .. warning:: Because of its internal implementation, you must explicitly set
       callbacks for new requests when writing :class:`XMLFeedSpider`-based spiders;
       unexpected behaviour can occur otherwise.


XMLFeedSpider example
~~~~~~~~~~~~~~~~~~~~~

These spiders are pretty easy to use, let's have a look at one example:

.. skip: next
.. code-block:: python

    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 :class:`~scrapy.Item`.

CSVFeedSpider
-------------

.. class:: 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 :meth:`parse_row`.

   .. attribute:: delimiter

       A string with the separator character for each field in the CSV file
       Defaults to ``','`` (comma).

   .. attribute:: quotechar

       A string with the enclosure character for each field in the CSV file
       Defaults to ``'"'`` (quotation mark).

   .. attribute:: headers

       A list of the column names in the CSV file.

   .. method:: 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`` and ``process_results`` methods
       for pre- and post-processing purposes.

CSVFeedSpider example
~~~~~~~~~~~~~~~~~~~~~

Let's see an example similar to the previous one, but using a
:class:`CSVFeedSpider`:

.. skip: next
.. code-block:: python

    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:: 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`_.

    .. attribute:: 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.

    .. attribute:: 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.

    .. attribute:: 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.

    .. attribute:: 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 same ``url`` 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. With
        ``sitemap_alternate_links`` disabled, only ``http://example.com/`` would be
        retrieved.

        Default is ``sitemap_alternate_links`` disabled.

    .. method:: 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 filter ``entries`` by date:

        .. code-block:: python

            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``
          (see ``sitemap_alternate_links``)
        - namespaces are removed, so lxml tags named as ``{namespace}tagname`` become only ``tagname``

        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:

.. code-block:: python

    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:

.. code-block:: python

    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``:

.. code-block:: python

    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:

.. code-block:: python

    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 ...

.. _Sitemaps: https://www.sitemaps.org/index.html
.. _Sitemap index files: https://www.sitemaps.org/protocol.html#index
.. _robots.txt: https://www.robotstxt.org/
.. _TLD: https://en.wikipedia.org/wiki/Top-level_domain
.. _Scrapyd documentation: https://scrapyd.readthedocs.io/en/latest/
