Selenium vs Scrapy: Which One Should You Choose for Web Scraping?

Web scraping is a technique for extracting data from an online source. It provides you with structured data that can be stored in any format. This data can then be used in AI and ML algorithms. Web scraping can provide you with large volumes of clean data that are optimal for these algorithms.

There are various tools and libraries that can be used for web scraping. In this article we will focus on two of the most popular web scraping frameworks: Scrapy vs. Selenium. We will analyze both frameworks and then we will see which one is the best choice for your web scraping needs.

What's the Difference Between Selenium vs Scrapy?

The main difference between Selenium and Scrapy is that Selenium is a web browser automation and testing framework that can be used for web scraping. Scrapy is a framework specifically dedicated for web scraping and web crawling.

Selenium vs. Scrapy: Overview

Selenium for Web Scraping

You must be wondering: how can a test automation tool be used for web scraping? Selenium has a webdriver component that provides web scraping features. There are various methods and objects in Selenium WebDriver that are useful for web scraping. There are:

1. WebDriver.page_source

This method returns the HTML code of the page.

2. WebDriver.title

Gives the title of the page.

3. WebDriver.current_url

Used to get the current URL of the page. 

4. Find_elements

Get a list of specific elements on a page. You can find an element by its name, class_name, tag, id, xpath. 

5. Web_Element

To get particular data from HTML elements, Web_Element is used. Web_Element.text,Web_Element,click(),web_Element.get_attribute(),Web_Element.send_keys() are few useful features in Web_Element

6. Is_displayed()

A method used to find out if an element is present on a page. It returns true if an element is present and vice versa.

What Is Scrapy?

Scrapy is a web scraping and web crawling framework designed to get structured data from websites. However, Scrapy can also be used for monitoring and automated testing web applications. Scrapy was developed in 2008 by “ScrapingHub.Ltd” and is written entirely in Python. Scrapy provides an asynchronous mechanism which processes multiple requests in parallel.

Scrapy for Web Scraping: Features

Here’s a list of the main built-in Scrapy features that make it a powerful web scraping tool:

1. Spiders

Spiders are classes that define a set of instructions to scrape a particular website. These built-in customized classes provide an efficient approach for web scraping.

2. Selectors

Selectors in scrapy are used to select parts of an HTML document defined by XPath or CSS expressions. With selectors you can use regular expressions through the re() method.

3. Items

Data extracted through spiders is returned as items. The itemadapter library supports the following items: attrs objects, dictionaries, item object, data class object.

4. Item Pipeline

A python class that validates, cleans and stores the scraped data in a database. In addition to this it also checks for duplicates.

5. Requests and Responses

Requests are generated from the spider that takes the request to the end point, where the request is executed and the response object takes the issued request to spider.

6. Link Extractors

A powerful feature that extracts links from responses.

Scrapy Built-in Services

Scrapy also provides following built-in services to automate tasks when scraping:

• Logging 
• Stats collection
• Sending emails
• Telnet console
• Web service

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Selenium for Web Scraping: Pros and Cons

Selenium Advantages

• Free and open source
• Provides multi-browser support
• Supports Linux, Windows and MAC OS 
• Multiple language support like Java, c#, Python, Kotlin, Ruby, Javascript

Selenium Disadvantages

• Selenium WebDriver occupies system resources even for small data set
• The scraping process begins once page is fully loaded so it is slow in terms of processing
• For each browser you need to install a WebDriver component

Scrapy: Pros and Cons

Scrapy Advantages

• Scrapy can extract data in different formats such as CSV, XML and JSON.
• Scrapy provides AutoThrottle features that automatically adjust the tool to the ideal crawling speed.  
• Scrapy is asynchronous so it can load several pages in parallel.
• Large volumes of data can be extracted 
• In terms of speed, Scrapy is fast
• Scrapy consumes little memory and CPU space

Scrapy Disadvantages

• Scrapy cannot handle Javascript 
• The installation process varies for different operating systems
• Scrapy requires Python version 2.7.+

Which Is Best — Selenium or Scrapy?

When it comes to selecting only one library, Selenium or Scrapy, the decision ultimately boils down to the nature of the use cases. Each library has its own pros and cons. Selenium is primarily a web automation tool, however, Selenium WebDrivers can also be used to scrape data from websites, if you’re already using it or you’re scraping a JS website. On the other hand, Scrapy is a powerful web-scraping framework that can be used for scraping huge volumes of data from different websites.

Let’s see some examples about when to choose each:

Data Volumes

Let’s say we are working on a project where we need large volumes of data from different websites. To scrape those websites we have to make multiple calls using proxies and VPNs. In addition to this we need a robust mechanism and we can’t afford delays. In such scenarios, Scrapy is an ideal choice. Using Scrapy you can easily work with proxies and VPNs. It can pull large volumes of data since it is a specialized web scraping framework. 

JavaScript Support

To scrape data from a website that uses Javascript, Selenium is a better approach. However, you can use Scrapy to scrape JavaScript-based websites through the Splash library.

Performance

Scrapy is asynchronous, it executes multiple requests simultaneously. Even if a request fails or any errors happen the incoming requests aren't affected. This improves the overall speed efficiency of the process. Selenium is also robust but in case of large data volume the overall process is slow.

Scrapy vs. Selenium Comparison Table

Conclusion

To conclude the above discussion I would say that both Selenium and Scrapy are powerful tools. The nature of work for which they’re originally developed is different from one another. Selenium is an excellent automation tool and Scrapy is by far the most robust web scraping framework. When we consider web scraping, in terms of speed and efficiency Scrapy is a better choice. While dealing with JavaScript based websites where we need to make AJAX/PJAX requests, Selenium can work better. I hope you got a clear understanding of Selenium vs. Scrapy and you are ready for your next project.

To learn more about using Selenium, check out this blog.

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