Scrapy is a powerful Python web scraping framework with many built-in features. Its main advantage over other web scraping tools is its asynchronous processing, which lets it run multiple requests at the same time. This is particularly useful for crawling large websites.
A Scrapy project is a set of configuration files and pieces of code that tells Scrapy what to do on a particular website. Each spider is an instance of this project and contains a callback function that takes a URL and returns the page.
Spiders can be configured to send requests in multiple ways, each with its own callback function. These functions can be written in any language, but they are best written in Python, which is the primary language used by Scrapy.
You can also use XPath or CSS selectors to define the elements on a webpage that you want to scrape. This allows you to create a spider that extracts the exact data you need without needing to write spider codes every single time.
Using XPath or CSS selectors, you can extract the data you need from a page, and store it in a format that is appropriate for your needs (CSS, JSON, or XML). Then, you can export this data in a variety of formats using a feed exporter.
Once you have your data in an appropriate format, you can save it to a file or write a pipeline to store it in a database. Then, you can use it as a basis for your analysis.
When scraping large amounts of data, it is often important to have the data in several different formats for analysis purposes. This can be done with Scrapy’s feed exporter, which allows you to export your scraped data in a variety of formats and then store it on the internet or in a database.
To use the feed exporter, you need to define the FEED_FORMAT and FEED_URI settings. Typically, these are the URLs to which you want your scraped data exported to.
Another important setting for Scrapy is ROBOTSTXT_OBEY. This read more setting tells Scrapy to wait at least 5 seconds between each new request it makes, which is a good way of ensuring that you don’t hurt the web server by repeatedly sending too many concurrent requests.
Finally, it is important to remember that you should treat any site you scrape politely. This means that you should not try to repurpose the content you scraped for your own purposes or spam the site with it.
For example, if you scrape StackOverflow, you need to make sure you keep ROBOTSTXT_OBEY True to ensure your IP address stays within the site’s limits. If you scrape StackOverflow without setting this value, your IP may get banned from the site!
The asynchronous processing of Scrapy also means that you can scrape hundreds or even thousands of pages at once. This is especially beneficial for crawling big websites, where the number of concurrent requests can be enormous. Fortunately, Scrapy’s scheduler allows you to handle these huge amounts of requests in a fault-tolerant manner.
