Scrapy Auto – What is Scrapy Auto?

Scrapy auto is an extension for Scrapy that allows you to impose throttling parameters on the crawler’s download rate. You can set the AUTOTHROTTLE_TARGET_CONCURRENCY option to specify a target value at which the crawler should try to approach. This value is used in conjunction with the CONCURRENT_REQUESTS_PER_DOMAIN and CONCURRENT_REQUESTS_PER_IP options to determine how many concurrent requests are being sent.

This is especially useful if you’re working on large projects that need to be completed quickly, or when you’re testing your spiders on real world websites. You can also use this feature to help ensure that the scraping process doesn’t saturate your server resources, or otherwise negatively impact other users.

When a new spider is created, the first step is to define which websites it will crawl. This can be done using the start_urls parameter, and it will automatically connect to each of them and call back the parse() method for each incoming page.

The parse() method will then take the response variable as its input and return whatever it’s instructed to scrape from the incoming page. Once it’s completed, Scrapy will pass the scraped data to item containers for temporary storage.

These item containers are akin to Python dictionaries in that they can contain multiple fields to store the individual elements of the data you’re extracting from the web pages. You can then use them to output the scraped data in several different ways, including XML, CSS and JSON formats.

XPath, CSS Selectors and Regular Expression support

Using extended XPath and CSS selectors, you can select which parts of a web page to extract. This is very useful if you’re working with complex URLs that may contain many types of elements.

Scrapy provides a handy interactive shell that you can use to debug and test your Xpath and CSS expressions. It’s great for ensuring that your XPath and CSS expressions are working correctly before you run your spiders.

Concurrent Requests

Scrapy’s asynchronous nature means that it doesn’t have to wait for one request to complete before it can run another, which is very helpful when crawling large websites or in situations where you need to process a lot of information simultaneously. The ability to run requests in parallel can greatly increase speed, and reduces the amount of time it takes for you to collect all the data you need.

Asynchronousness is a very important feature for web scraping because it can save a lot of time on long crawls, as well as make your robot more robust against errors or problems. Selenium is very similar to Scrapy in this regard, but it can be slower on some occasions, particularly when running a big set of crawls.

It is therefore very important to treat any site you scrape carefully – don’t use it maliciously, or else you could end up getting a rate limit from the server, which can be a serious hassle. This can be avoided by setting ROBOTSTXT_OBEY = True in the spider, which will prevent your crawl from going beyond its configured bounds.