Shell file download web site - something
Scrapy shell¶
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 or CSS 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 expressions 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.
Configuring the shell¶
If you have IPython installed, the Scrapy shell will use it (instead of the standard Python console). The IPython console is much more powerful and provides smart auto-completion and colorized output, among other things.
We highly recommend you install IPython, specially if you’re working on Unix systems (where IPython excels). See the IPython installation guide for more info.
Scrapy also has support for bpython, and will try to use it where IPython is unavailable.
Through Scrapy’s settings you can configure it to use any one of , or the standard shell, regardless of which are installed. This is done by setting the environment variable; or by defining it in your scrapy.cfg:
Launch the shell¶
To launch the Scrapy shell you can use the command like this:
Where the is the URL you want to scrape.
also works for local files. This can be handy if you want to play around with a local copy of a web page. understands the following syntaxes for local files:
Note
When using relative file paths, be explicit and prepend them with (or when relevant). will not work as one might expect (and this is by design, not a bug).
Because favors HTTP URLs over File URIs, and being syntactically similar to , will treat as a domain name and trigger a DNS lookup error:
will not test beforehand if a file called exists in the current directory. Again, be explicit.
Using the shell¶
The Scrapy shell is just a regular Python console (or IPython console if you have it available) which provides some additional shortcut functions for convenience.
Available Shortcuts¶
- print a help with the list of available objects and shortcuts
- fetch a new response from the given URL and update all related objects accordingly. You can optionaly ask for HTTP 3xx redirections to not be followed by passing
- fetch a new response from the given request and update all related objects accordingly.
- 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.
Available Scrapy objects¶
The Scrapy shell automatically creates some convenient objects from the downloaded page, like the object and the objects (for both HTML and XML content).
Those objects are:
- the current object.
- the Spider which is known to handle the URL, or a object if there is no spider found for the current URL
- a object of the last fetched page. You can modify this request using or fetch a new request (without leaving the shell) using the shortcut.
- a object containing the last fetched page
- the current Scrapy settings
Example of shell session¶
Here’s an example of a typical shell session where we start by scraping the https://scrapy.org page, and then proceed to scrape the https://old.reddit.com/ page. Finally, we modify the (Reddit) request method to POST and re-fetch it getting an 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:
Note
Remember to always enclose URLs in quotes when running the Scrapy shell from the command line, otherwise URLs containing arguments (i.e. the character) will not work.
On Windows, use double quotes instead:
Then, the shell fetches the URL (using the Scrapy downloader) and prints the list of available objects and useful shortcuts (you’ll notice that these lines all start with the prefix):
After that, we can start playing with the objects:
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 function.
Here’s an example of how you would call it from your spider:
When you run the spider, you will get something similar to this:
Then, you can check if the extraction code is working:
Nope, it doesn’t. So you can open the response in your web browser and see if it’s the response you were expecting:
Finally you hit Ctrl-D (or Ctrl-Z in Windows) to exit the shell and resume the crawling:
Note that you can’t use the 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.
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