The Scrapy shell is an interactive shell where you can try and debug your scraping code very quickly, without having to run the spider. It’s meant to be used for testing data extraction code, but you can actually use it for testing any kind of code as it is also a regular Python shell.
The shell is used for testing XPath expressions and see how they work and what data they extract from the web pages you’re trying to scrape. It allows you to interactively test your XPaths while you’re writing your spider, without having to run the spider to test every change.
Once you get familiarized with the Scrapy shell you’ll see that it’s an invaluable tool for developing and debugging your spiders.
If you have IPython installed, the Scrapy shell will use it (instead of the standard Python console). The IPython console is a much more powerful and provides smart auto-completion and colorized output, among other things.
Launch the shell¶
To launch the shell type:
scrapy-ctl.py shell <url>
<url> is the URL you want to scrape.
Using the shell¶
The Scrapy shell is just a regular Python console (or IPython shell if you have it available) which provides some additional functions available by default (as shortcuts):
shelp()- print a help with the list of available objects and shortcuts
fetch(request_or_url)- fetch a new response from the given request or URL and update all related objects accordingly.
view(response)- open the given response in your local web browser, for inspection. This will add a <base> tag to the response body in order for external links (such as images and style sheets) to display properly. Note, however,that this will create a temporary file in your computer, which won’t be removed automatically.
Those objects are:
url- the URL being analyzed
spider- the Spider which is known to handle the URL, or a
BaseSpiderobject if there is no spider is found for the current URL
Requestobject of the last fetched page. You can modify this request using
replace()fetch a new request (without leaving the shell) using the
Responseobject containing the last fetched page
HtmlXPathSelectorobject constructed with the last response fetched
XmlXPathSelectorobject constructed with the last response fetched
Example of shell session¶
Here’s an example of a typical shell session where we start by scraping the http://scrapy.org page, and then proceed to scrape the http://slashdot.org page. Finally, we modify the (Slashdot) request method to POST and re-fetch it getting a HTTP 405 (method not allowed) error. We end the session by typing Ctrl-D (in Unix systems) or Ctrl-Z in Windows.
Keep in mind that the data extracted here may not be the same when you try it, as those pages are not static and could have changed by the time you test this. The only purpose of this example is to get you familiarized with how the Scrapy shell works.
First, we launch the shell:
python scrapy-ctl.py shell http://scrapy.org --nolog
Then, the shell fetches the url (using the Scrapy downloader) and prints the list of available objects and some help:
Fetching <http://scrapy.org>... Available objects ================= xxs : <XmlXPathSelector (http://scrapy.org) xpath=None> url : http://scrapy.org request : <http://scrapy.org> spider : <scrapy.spider.models.BaseSpider object at 0x2bed9d0> hxs : <HtmlXPathSelector (http://scrapy.org) xpath=None> item : Item() response : <http://scrapy.org> Available shortcuts =================== shelp() : Prints this help. fetch(req_or_url) : Fetch a new request or URL and update objects view(response) : View response in a browser Python 2.6.2 (release26-maint, Apr 19 2009, 01:58:18) Type "help", "copyright", "credits" or "license" for more information. >>>
After that, we can stary playing with the objects:
>>> hxs.select("//h2/text()").extract() u'Welcome to Scrapy' >>> fetch("http://slashdot.org") Fetching <http://slashdot.org>... Done - use shelp() to see available objects >>> hxs.select("//h2/text()").extract() [u'News for nerds, stuff that matters'] >>> request = request.replace(method="POST") >>> fetch(request) Fetching <POST http://slashdot.org>... 2009-04-03 00:57:39-0300 [scrapybot] ERROR: Downloading <http://slashdot.org> from <None>: 405 Method Not Allowed >>>
Invoking the shell from spiders to inspect responses¶
Sometimes you want to inspect the responses that are being processed in a certain point of your spider, if only to check that response you expect is getting there.
This can be achieved by using the
Here’s an example of how you would call it from your spider:
class MySpider(BaseSpider): ... def parse(self, response): if response.url == 'http://www.example.com/products.php': from scrapy.shell import inspect_response inspect_response(response) # ... your parsing code ..
When you the spider you will get something similar to this:
2009-08-27 19:15:25-0300 [example.com] DEBUG: Crawled <http://www.example.com/> (referer: <None>) 2009-08-27 19:15:26-0300 [example.com] DEBUG: Crawled <http://www.example.com/products.php> (referer: <http://www.example.com/>) Scrapy Shell ============ Inspecting: <http://www.example.com/products.php Use shelp() to see available objects Python 2.6.2 (release26-maint, Apr 19 2009, 01:58:18) [GCC 4.3.3] on linux2 Type "help", "copyright", "credits" or "license" for more information. (InteractiveConsole) >>> response.url 'http://www.example.com/products.php'
Then, you can check if the extraction code is working:
>>> hxs.select('//h1') 
Nope, it doesn’t. So you can open the response in your web browser and see if it’s the response you were expecting:
>>> view(response) >>>
Finally you hit Ctrl-D (or Ctrl-Z in Windows) to exit the shell and resume the crawling:
>>> ^D 2009-08-27 19:15:25-0300 [example.com] DEBUG: Crawled <http://www.example.com/product.php?id=1> (referer: <None>) 2009-08-27 19:15:25-0300 [example.com] DEBUG: Crawled <http://www.example.com/product.php?id=2> (referer: <None>) # ...
Note that you can’t use the
fetch shortcut here since the Scrapy engine is
blocked by the shell. However, after you leave the shell, the spider will
continue crawling where it stopped, as shown above.