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<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> </head>

Scrapy Tutorial

In this tutorial, we'll assume that Scrapy is already installed on your system. If that's not the case, see :ref:`intro-install`.

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We are going to use Open directory project (dmoz) as our example domain to scrape.

This tutorial will walk you through these tasks:

  1. Creating a new Scrapy project

  2. Defining the Items you will extract

  3. Writing a :ref:`spider <topics-spiders>` to crawl a site and extract :ref:`Items <topics-items>`

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  4. Writing an :ref:`Item Pipeline <topics-item-pipeline>` to store the extracted Items

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Scrapy is written in Python. If you're new to the language you might want to start by getting an idea of what the language is like, to get the most out of Scrapy. If you're already familiar with other languages, and want to learn Python quickly, we recommend Learn Python The Hard Way. If you're new to programming and want to start with Python, take a look at this list of Python resources for non-programmers.

Creating a project

Before you start scraping, you will have to set up a new Scrapy project. Enter a directory where you'd like to store your code and run:

scrapy startproject tutorial

This will create a tutorial directory with the following contents:

tutorial/
    scrapy.cfg
    tutorial/
        __init__.py
        items.py
        pipelines.py
        settings.py
        spiders/
            __init__.py
            ...

These are basically:

  • scrapy.cfg: the project configuration file
  • tutorial/: the project's python module, you'll later import your code from here.
  • tutorial/items.py: the project's items file.
  • tutorial/pipelines.py: the project's pipelines file.
  • tutorial/settings.py: the project's settings file.
  • tutorial/spiders/: a directory where you'll later put your spiders.

Defining our Item

Items are containers that will be loaded with the scraped data; they work like simple python dicts but provide additional protection against populating undeclared fields, to prevent typos.

They are declared by creating a :class:`scrapy.Item <scrapy.item.Item>` class and defining its attributes as :class:`scrapy.Field <scrapy.item.Field>` objects, much like in an ORM (don't worry if you're not familiar with ORMs, you will see that this is an easy task).

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We begin by modeling the item that we will use to hold the site's data obtained from dmoz.org. As we want to capture the name, url and description of the sites, we define fields for each of these three attributes. To do that, we edit items.py, found in the tutorial directory. Our Item class looks like this:

import scrapy

class DmozItem(scrapy.Item):
    title = scrapy.Field()
    link = scrapy.Field()
    desc = scrapy.Field()

This may seem complicated at first, but defining the item allows you to use other handy components of Scrapy that need to know what does your item look like.

Our first Spider

Spiders are user-written classes used to scrape information from a domain (or group of domains).

They define an initial list of URLs to download, how to follow links, and how to parse the contents of pages to extract :ref:`items <topics-items>`.

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To create a Spider, you must subclass :class:`scrapy.Spider <scrapy.spider.Spider>` and define the three main mandatory attributes:

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  • :attr:`~scrapy.spider.Spider.name`: identifies the Spider. It must be unique, that is, you can't set the same name for different Spiders.

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  • :attr:`~scrapy.spider.Spider.start_urls`: a list of URLs where the Spider will begin to crawl from. The first pages downloaded will be those listed here. The subsequent URLs will be generated successively from data contained in the start URLs.

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  • :meth:`~scrapy.spider.Spider.parse`: a method of the spider, which will be called with the downloaded :class:`~scrapy.http.Response` object of each start URL. The response is passed to the method as the first and only argument.

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    This method is responsible for parsing the response data and extracting scraped data (as scraped items) and more URLs to follow.

    The :meth:`~scrapy.spider.Spider.parse` method is in charge of processing the response and returning scraped data (as :class:`~scrapy.item.Item` objects) and more URLs to follow (as :class:`~scrapy.http.Request` objects).

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This is the code for our first Spider; save it in a file named dmoz_spider.py under the tutorial/spiders directory:

import scrapy

class DmozSpider(scrapy.Spider):
    name = "dmoz"
    allowed_domains = ["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):
        filename = response.url.split("/")[-2]
        with open(filename, 'wb') as f:
            f.write(response.body)

Crawling

To put our spider to work, go to the project's top level directory and run:

scrapy crawl dmoz

The crawl dmoz command runs the spider for the dmoz.org domain. You will get an output similar to this:

2014-01-23 18:13:07-0400 [scrapy] INFO: Scrapy started (bot: tutorial)
2014-01-23 18:13:07-0400 [scrapy] INFO: Optional features available: ...
2014-01-23 18:13:07-0400 [scrapy] INFO: Overridden settings: {}
2014-01-23 18:13:07-0400 [scrapy] INFO: Enabled extensions: ...
2014-01-23 18:13:07-0400 [scrapy] INFO: Enabled downloader middlewares: ...
2014-01-23 18:13:07-0400 [scrapy] INFO: Enabled spider middlewares: ...
2014-01-23 18:13:07-0400 [scrapy] INFO: Enabled item pipelines: ...
2014-01-23 18:13:07-0400 [dmoz] INFO: Spider opened
2014-01-23 18:13:08-0400 [dmoz] DEBUG: Crawled (200) <GET http://www.dmoz.org/Computers/Programming/Languages/Python/Resources/> (referer: None)
2014-01-23 18:13:09-0400 [dmoz] DEBUG: Crawled (200) <GET http://www.dmoz.org/Computers/Programming/Languages/Python/Books/> (referer: None)
2014-01-23 18:13:09-0400 [dmoz] INFO: Closing spider (finished)

Pay attention to the lines containing [dmoz], which correspond to our spider. You can see a log line for each URL defined in start_urls. Because these URLs are the starting ones, they have no referrers, which is shown at the end of the log line, where it says (referer: None).

But more interestingly, as our parse method instructs, two files have been created: Books and Resources, with the content of respective URLs.

What just happened under the hood?

Scrapy creates :class:`scrapy.Request <scrapy.http.Request>` objects for each URL in the start_urls attribute of the Spider, and assigns them the parse method of the spider as their callback function.

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These Requests are scheduled, then executed, and :class:`scrapy.http.Response` objects are returned and then fed back to the spider, through the :meth:`~scrapy.spider.Spider.parse` method.

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Extracting Items

Introduction to Selectors

There are several ways to extract data from web pages. Scrapy uses a mechanism based on XPath or CSS expressions called :ref:`Scrapy Selectors <topics-selectors>`. For more information about selectors and other extraction mechanisms see the :ref:`Selectors documentation <topics-selectors>`.

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Here are some examples of XPath expressions and their meanings:

  • /html/head/title: selects the <title> element, inside the <head> element of an HTML document
  • /html/head/title/text(): selects the text inside the aforementioned <title> element.
  • //td: selects all the <td> elements
  • //div[@class="mine"]: selects all div elements which contain an attribute class="mine"

These are just a couple of simple examples of what you can do with XPath, but XPath expressions are indeed much more powerful. To learn more about XPath we recommend this XPath tutorial.

For working with XPaths, Scrapy provides :class:`~scrapy.selector.Selector` class and convenient shortcuts to avoid instantiating selectors yourself every time you need to select something from a response.

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You can see selectors as objects that represent nodes in the document structure. So, the first instantiated selectors are associated with the root node, or the entire document.

Selectors have four basic methods (click on the method to see the complete API documentation):

Trying Selectors in the Shell

To illustrate the use of Selectors we're going to use the built-in :ref:`Scrapy shell <topics-shell>`, which also requires IPython (an extended Python console) installed on your system.

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To start a shell, you must go to the project's top level directory and run:

scrapy shell "http://www.dmoz.org/Computers/Programming/Languages/Python/Books/"

Note

Remember to always enclose urls in quotes when running Scrapy shell from command-line, otherwise urls containing arguments (ie. & character) will not work.

This is what the shell looks like:

[ ... Scrapy log here ... ]

2014-01-23 17:11:42-0400 [default] DEBUG: Crawled (200) <GET http://www.dmoz.org/Computers/Programming/Languages/Python/Books/> (referer: None)
[s] Available Scrapy objects:
[s]   crawler    <scrapy.crawler.Crawler object at 0x3636b50>
[s]   item       {}
[s]   request    <GET http://www.dmoz.org/Computers/Programming/Languages/Python/Books/>
[s]   response   <200 http://www.dmoz.org/Computers/Programming/Languages/Python/Books/>
[s]   settings   <scrapy.settings.Settings object at 0x3fadc50>
[s]   spider     <Spider 'default' at 0x3cebf50>
[s] Useful shortcuts:
[s]   shelp()           Shell help (print this help)
[s]   fetch(req_or_url) Fetch request (or URL) and update local objects
[s]   view(response)    View response in a browser

In [1]:

After the shell loads, you will have the response fetched in a local response variable, so if you type response.body you will see the body of the response, or you can type response.headers to see its headers.

More importantly response has a selector attribute which is an instance of :class:`~scrapy.selector.Selector` class, instantiated with this particular response. You can run queries on response by calling response.selector.xpath() or response.selector.css(). There are also some convenience shortcuts like response.xpath() or response.xml() which map directly to response.selector.xpath() and response.selector.css().

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So let's try it:

In [1]: response.xpath('//title')
Out[1]: [<Selector xpath='//title' data=u'<title>Open Directory - Computers: Progr'>]

In [2]: response.xpath('//title').extract()
Out[2]: [u'<title>Open Directory - Computers: Programming: Languages: Python: Books</title>']

In [3]: response.xpath('//title/text()')
Out[3]: [<Selector xpath='//title/text()' data=u'Open Directory - Computers: Programming:'>]

In [4]: response.xpath('//title/text()').extract()
Out[4]: [u'Open Directory - Computers: Programming: Languages: Python: Books']

In [5]: response.xpath('//title/text()').re('(\w+):')
Out[5]: [u'Computers', u'Programming', u'Languages', u'Python']

Extracting the data

Now, let's try to extract some real information from those pages.

You could type response.body in the console, and inspect the source code to figure out the XPaths you need to use. However, inspecting the raw HTML code there could become a very tedious task. To make it easier, you can use Firefox Developer Tools or some Firefox extensions like Firebug. For more information see :ref:`topics-firebug` and :ref:`topics-firefox`.

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After inspecting the page source, you'll find that the web site's information is inside a <ul> element, in fact the second <ul> element.

So we can select each <li> element belonging to the site's list with this code:

response.xpath('//ul/li')

And from them, the site's descriptions:

response.xpath('//ul/li/text()').extract()

The site's titles:

response.xpath('//ul/li/a/text()').extract()

And the site's links:

response.xpath('//ul/li/a/@href').extract()

As we've said before, each .xpath() call returns a list of selectors, so we can concatenate further .xpath() calls to dig deeper into a node. We are going to use that property here, so:

for sel in response.xpath('//ul/li'):
    title = sel.xpath('a/text()').extract()
    link = sel.xpath('a/@href').extract()
    desc = sel.xpath('text()').extract()
    print title, link, desc

Note

For a more detailed description of using nested selectors, see :ref:`topics-selectors-nesting-selectors` and :ref:`topics-selectors-relative-xpaths` in the :ref:`topics-selectors` documentation

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Let's add this code to our spider:

import scrapy

class DmozSpider(scrapy.Spider):
    name = "dmoz"
    allowed_domains = ["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):
        for sel in response.xpath('//ul/li'):
            title = sel.xpath('a/text()').extract()
            link = sel.xpath('a/@href').extract()
            desc = sel.xpath('text()').extract()
            print title, link, desc

Now try crawling dmoz.org again and you'll see sites being printed in your output. Run:

scrapy crawl dmoz

Using our item

:class:`~scrapy.item.Item` objects are custom python dicts; you can access the values of their fields (attributes of the class we defined earlier) using the standard dict syntax like:

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>>> item = DmozItem()
>>> item['title'] = 'Example title'
>>> item['title']
'Example title'

Spiders are expected to return their scraped data inside :class:`~scrapy.item.Item` objects. So, in order to return the data we've scraped so far, the final code for our Spider would be like this:

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import scrapy

from tutorial.items import DmozItem

class DmozSpider(scrapy.Spider):
    name = "dmoz"
    allowed_domains = ["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):
        for sel in response.xpath('//ul/li'):
            item = DmozItem()
            item['title'] = sel.xpath('a/text()').extract()
            item['link'] = sel.xpath('a/@href').extract()
            item['desc'] = sel.xpath('text()').extract()
            yield item

Note

You can find a fully-functional variant of this spider in the dirbot project available at https://github.com/scrapy/dirbot

Now crawling dmoz.org yields DmozItem objects:

[dmoz] DEBUG: Scraped from <200 http://www.dmoz.org/Computers/Programming/Languages/Python/Books/>
     {'desc': [u' - By David Mertz; Addison Wesley. Book in progress, full text, ASCII format. Asks for feedback. [author website, Gnosis Software, Inc.\n],
      'link': [u'http://gnosis.cx/TPiP/'],
      'title': [u'Text Processing in Python']}
[dmoz] DEBUG: Scraped from <200 http://www.dmoz.org/Computers/Programming/Languages/Python/Books/>
     {'desc': [u' - By Sean McGrath; Prentice Hall PTR, 2000, ISBN 0130211192, has CD-ROM. Methods to build XML applications fast, Python tutorial, DOM and SAX, new Pyxie open source XML processing library. [Prentice Hall PTR]\n'],
      'link': [u'http://www.informit.com/store/product.aspx?isbn=0130211192'],
      'title': [u'XML Processing with Python']}

Storing the scraped data

The simplest way to store the scraped data is by using :ref:`Feed exports <topics-feed-exports>`, with the following command:

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scrapy crawl dmoz -o items.json

That will generate an items.json file containing all scraped items, serialized in JSON.

In small projects (like the one in this tutorial), that should be enough. However, if you want to perform more complex things with the scraped items, you can write an :ref:`Item Pipeline <topics-item-pipeline>`. As with Items, a placeholder file for Item Pipelines has been set up for you when the project is created, in tutorial/pipelines.py. Though you don't need to implement any item pipelines if you just want to store the scraped items.

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Next steps

This tutorial covered only the basics of Scrapy, but there's a lot of other features not mentioned here. Check the :ref:`topics-whatelse` section in :ref:`intro-overview` chapter for a quick overview of the most important ones.

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Then, we recommend you continue by playing with an example project (see :ref:`intro-examples`), and then continue with the section :ref:`section-basics`.

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