Locally, while developing a scraper you can use Scrapy's built-in cache system. Hopefully, Scrapy provides caching to speed-up development and concurrent requests for production runs. When scraping multiple pages, it makes the scraper significantly slower. There are two challenges with headless browsers: they are slower and hard to scale.Įxecuting JavaScript in a headless browser and waiting for all network calls can take several seconds per page. However, to execute JavaScript code you need to resolve requests with a real browser or a headless browser. Twisted makes Scrapy fast and able to scrape multiple pages concurrently. Scrapy uses Twisted under the hood, an asynchronous networking framework. Using Scrapy cache and concurrency to scrape faster You can run an instance of Splash locally with Docker. Since then, other popular projects such as PhantomJS have been discontinued in favour of Firefox, Chrome and Safari headless browsers. Splash was created in 2013, before headless Chrome and other major headless browsers were released in 2017. It’s maintained by Scrapinghub, the main contributor to Scrapy and integrated with Scrapy through the scrapy-splash middleware. Splash is a web browser as a service with an API. Executing JavaScript in Scrapy with Splash Next, I will compare two solutions to execute JavaScript with Scrapy at scale. On production, the main issue with scrapy-selenium is that there is no trivial way to set up a Selenium grid to have multiple browser instances running on remote machines. SeleniumRequest takes some additional arguments such as wait_time to wait before returning the response, wait_until to wait for an HTML element, screenshot to take a screenshot and script for executing a custom JavaScript script. You can then configure Selenium on your Scrapy project settings. For example, Firefox requires you to install geckodriver. Selenium needs a web driver to interact with a browser. Selenium is a framework to interact with browsers commonly used for testing applications, web scraping and taking screenshots. Locally, you can interact with a headless browser with Scrapy with the scrapy-selenium middleware. Executing JavaScript in Scrapy with Selenium Once configured in your project settings, instead of yielding a normal Scrapy Request from your spiders, you yield a SeleniumRequest, SplashRequest or ScrapingBeeRequest. I’ve used three libraries to execute JavaScript with Scrapy: scrapy-selenium, scrapy-splash and scrapy-scrapingbee.Īll three libraries are integrated as a Scrapy downloader middleware. Scrapy middlewares for headless browsersĪ headless browser is a web browser without a graphical user interface. But to scrape client-side data directly from the HTML you first need to execute the JavaScript code. While these hacks may work on some websites, I find the code harder to understand and maintain than traditional XPATHs. I’ve often found myself inspecting API requests on the browser network tools and extracting data from JavaScript variables. Scraping client-side rendered websites with Scrapy used to be painful. In this article, I compare the most popular solutions to execute JavaScript with Scrapy, how to scale headless browsers and introduce an open-source integration with ScrapingBee API for JavaScript support and proxy rotation. If you're new to scrapy, you should probably begin by reading this great tutorial that will teach you all the basics of Scrapy. In exchange, Scrapy takes care of concurrency, collecting stats, caching, handling retrial logic and many others. Compared to other Python scraping libraries, such as Beautiful Soup, Scrapy forces you to structure your code based on some best practices. Scrapy is a popular Python web scraping framework. I’ve scraped hundreds of sites, and I always use Scrapy. Scraping data from a dynamic website without server-side rendering often requires executing JavaScript code. Most modern websites use a client-side JavaScript framework such as React, Vue or Angular.
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