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Frequently Asked Questions

How does Scrapy compare to BeautifulSoup or lxml?

BeautifulSoup and lxml are libraries for parsing HTML and XML. Scrapy is an application framework for writing web spiders that crawl web sites and extract data from them.

Scrapy provides a built-in mechanism for extracting data (called :ref:`selectors <topics-selectors>`) but you can easily use BeautifulSoup (or lxml) instead, if you feel more comfortable working with them. After all, they're just parsing libraries which can be imported and used from any Python code.

In other words, comparing BeautifulSoup (or lxml) to Scrapy is like comparing jinja2 to Django.

What Python versions does Scrapy support?

Scrapy runs in Python 2.6 and 2.7.

Does Scrapy work with Python 3.0?

No, and there are no plans to port Scrapy to Python 3.0 yet. At the moment, Scrapy works with Python 2.6 and 2.7.

Did Scrapy "steal" X from Django?

Probably, but we don't like that word. We think Django is a great open source project and an example to follow, so we've used it as an inspiration for Scrapy.

We believe that, if something is already done well, there's no need to reinvent it. This concept, besides being one of the foundations for open source and free software, not only applies to software but also to documentation, procedures, policies, etc. So, instead of going through each problem ourselves, we choose to copy ideas from those projects that have already solved them properly, and focus on the real problems we need to solve.

We'd be proud if Scrapy serves as an inspiration for other projects. Feel free to steal from us!

Does Scrapy work with HTTP proxies?

Yes. Support for HTTP proxies is provided (since Scrapy 0.8) through the HTTP Proxy downloader middleware. See :class:`~scrapy.contrib.downloadermiddleware.httpproxy.HttpProxyMiddleware`.

Scrapy crashes with: ImportError: No module named win32api

You need to install pywin32 because of this Twisted bug.

How can I simulate a user login in my spider?

See :ref:`topics-request-response-ref-request-userlogin`.

Does Scrapy crawl in breath-first or depth-first order?

By default, Scrapy uses a LIFO queue for storing pending requests, which basically means that it crawls in DFO order. This order is more convenient in most cases. If you do want to crawl in true BFO order, you can do it by setting the following settings:

DEPTH_PRIORITY = 1
SCHEDULER_DISK_QUEUE = 'scrapy.squeue.PickleFifoDiskQueue'
SCHEDULER_MEMORY_QUEUE = 'scrapy.squeue.FifoMemoryQueue'

My Scrapy crawler has memory leaks. What can I do?

See :ref:`topics-leaks`.

Also, Python has a builtin memory leak issue which is described in :ref:`topics-leaks-without-leaks`.

How can I make Scrapy consume less memory?

See previous question.

Can I use Basic HTTP Authentication in my spiders?

Yes, see :class:`~scrapy.contrib.downloadermiddleware.httpauth.HttpAuthMiddleware`.

Why does Scrapy download pages in English instead of my native language?

Try changing the default Accept-Language request header by overriding the :setting:`DEFAULT_REQUEST_HEADERS` setting.

Where can I find some example Scrapy projects?

See :ref:`intro-examples`.

Can I run a spider without creating a project?

Yes. You can use the :command:`runspider` command. For example, if you have a spider written in a my_spider.py file you can run it with:

scrapy runspider my_spider.py

See :command:`runspider` command for more info.

I get "Filtered offsite request" messages. How can I fix them?

Those messages (logged with DEBUG level) don't necessarily mean there is a problem, so you may not need to fix them.

Those message are thrown by the Offsite Spider Middleware, which is a spider middleware (enabled by default) whose purpose is to filter out requests to domains outside the ones covered by the spider.

For more info see: :class:`~scrapy.contrib.spidermiddleware.offsite.OffsiteMiddleware`.

What is the recommended way to deploy a Scrapy crawler in production?

See :ref:`topics-scrapyd`.

Can I use JSON for large exports?

It'll depend on how large your output is. See :ref:`this warning <json-with-large-data>` in :class:`~scrapy.contrib.exporter.JsonItemExporter` documentation.

Can I return (Twisted) deferreds from signal handlers?

Some signals support returning deferreds from their handlers, others don't. See the :ref:`topics-signals-ref` to know which ones.

What does the response status code 999 means?

999 is a custom reponse status code used by Yahoo sites to throttle requests. Try slowing down the crawling speed by using a download delay of 2 (or higher) in your spider:

class MySpider(CrawlSpider):

    name = 'myspider'

    DOWNLOAD_DELAY = 2

    # [ ... rest of the spider code ... ]

Or by setting a global download delay in your project with the :setting:`DOWNLOAD_DELAY` setting.

Can I call pdb.set_trace() from my spiders to debug them?

Yes, but you can also use the Scrapy shell which allows you too quickly analyze (and even modify) the response being processed by your spider, which is, quite often, more useful than plain old pdb.set_trace().

For more info see :ref:`topics-shell-inspect-response`.

Simplest way to dump all my scraped items into a JSON/CSV/XML file?

To dump into a JSON file:

scrapy crawl myspider -o items.json -t json

To dump into a CSV file:

scrapy crawl myspider -o items.csv -t csv

To dump into a XML file:

scrapy crawl myspider -o items.xml -t xml

For more information see :ref:`topics-feed-exports`

What's this huge cryptic __VIEWSTATE parameter used in some forms?

The __VIEWSTATE parameter is used in sites built with ASP.NET/VB.NET. For more info on how it works see this page. Also, here's an example spider which scrapes one of these sites.

What's the best way to parse big XML/CSV data feeds?

Parsing big feeds with XPath selectors can be problematic since they need to build the DOM of the entire feed in memory, and this can be quite slow and consume a lot of memory.

In order to avoid parsing all the entire feed at once in memory, you can use the functions xmliter and csviter from scrapy.utils.iterators module. In fact, this is what the feed spiders (see :ref:`topics-spiders`) use under the cover.

Does Scrapy manage cookies automatically?

Yes, Scrapy receives and keeps track of cookies sent by servers, and sends them back on subsequent requests, like any regular web browser does.

For more info see :ref:`topics-request-response` and :ref:`cookies-mw`.

How can I see the cookies being sent and received from Scrapy?

Enable the :setting:`COOKIES_DEBUG` setting.

How can I instruct a spider to stop itself?

Raise the :exc:`~scrapy.exceptions.CloseSpider` exception from a callback. For more info see: :exc:`~scrapy.exceptions.CloseSpider`.

How can I prevent my Scrapy bot from getting banned?

Some websites implement certain measures to prevent bots from crawling them, with varying degrees of sophistication. Getting around those measures can be difficult and tricky, and may sometimes require special infrastructure. Please consider contacting commercial support if in doubt.

Here are some tips to keep in mind when dealing with these kind of sites:

  • rotate your user agent from a pool of well-known ones from browsers (google around to get a list of them)
  • disable cookies (see :setting:`COOKIES_ENABLED`) as some sites may use cookies to spot bot behaviour
  • use download delays (2 or higher). See :setting:`DOWNLOAD_DELAY` setting.
  • is possible, use Google cache to fetch pages, instead of hitting the sites directly
  • use a pool of rotating IPs. For example, the free Tor project or paid services like ProxyMesh or ProxyHub.

If you are still unable to prevent your bot getting banned, consider contacting commercial support.

Should I use spider arguments or settings to configure my spider?

Both :ref:`spider arguments <spiderargs>` and :ref:`settings <topics-settings>` can be used to configure your spider. There is no strict rule that mandates to use one or the other, but settings are more suited for parameters that, once set, don't change much, while spider arguments are meant to change more often, even on each spider run and sometimes are required for the spider to run at all (for example, to set the start url of a spider).

To illustrate with an example, assuming you have a spider that needs to log into a site to scrape data, and you only want to scrape data from a certain section of the site (which varies each time). In that case, the credentials to log in would be settings, while the url of the section to scrape would be a spider argument.

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