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Tackling Pagination for Web Scraping

January 8, 2018Category : Blog
Tackling Pagination for Web Scraping

Web design is a dynamic space where coding best practices, standards and design trends change very often. While most of such changes are meant for the betterment of user experience for the visitors, bots often have a hard time navigating a webpage designed with humans in mind.

Navigating through different pages on a website is an integral part of the web scraping process and accounts for most of its automation prowess. However, when you’re on the tough road of web scraping, the pagination structure used by the websites can often be a tough nut to crack.

Pagination is a crucial element in web designing as it helps divide and present content in an easily digestible manner for the web visitors.

At PromptCloud, we have been handling websites of varying complexities including ones with a wide variety of pagination structures. If you’re trying to crawl data from a website and is in a dilemma about how to go about writing a crawler for different types of pagination, we’ve got you covered.

Numbered pagination with changing URL

Numbered pagination is perhaps one of the oldest and most used pagination systems on the web. The method to traverse through pages on a website with this type of navigation system is pretty straightforward. Get requests are used to fetch the pages after a loop is employed to make a list of the pages available on the site. Once the page URLs are compiled, a queuing system is used to automatically fetch the html data from each page. The real scraping happens on the offline pages saved this way.

Infinite scrolling using AJAX

Infinite scrolling is typically used by websites with a large amount of content to display. Clicking on next/previous buttons can be an exhausting activity for the user and infinite scrolling solves this problem by automatically loading new content as the user scrolls to the bottom of the page.  Infinite scrolling is being used by many popular websites including Twitter.

Since infinite scrolling pagination is typically powered by AJAX, fetching new pages becomes a challenging feat. In such cases, the best approach is to use a browser automation tool like Selenium to mimic human behavior, which is scrolling down in this case.

To extract new pages, Selenium has to be programmed to scroll down and count the number of new elements loaded. If the number is seen to have increased, the page can be saved. This activity has to be repeated until no new records are being loaded by the site.

AJAX based pagination where URL doesn’t change

There are some websites with a dynamic navigation system whereby new elements are loaded upon clicking on next/previous buttons. Unlike numbered pagination, the URL of the webpage doesn’t change in this case since content is loaded by AJAX calls in the background. Simply put, the webpage is acting like an app and loading the data on demand.

Browser automation is the way to go here again since it would be difficult to write a program from scratch to mimic those AJAX calls that are loading new content. Selenium can be programmed to click on the next button ‘n’ number of times where n is the number of pages available on the site.

AJAX based pagination where number of pages is not displayed

The approach here is very similar to that of AJAX based pagination where the page URL doesn’t change. However, since the number of pages is unknown the program has to keep clicking on the next button until the button disappears, which should load every page available on the site.

Load more button

Load more button type navigation is a very small variable of infinite scrolling. While the trigger for content loading is the page scroll in case of infinite scrolling, the user is required to click on a ‘Load more’ button in this case. Selenium is the right approach for this type of navigation as the content is being loaded using AJAX calls.

Conclusion

Navigation being a critical component of web scraping, has to be tackled using the best approach for maximum efficiency. If the navigation isn’t done right, your crawler can come to a halt, effectively causing loss of data and time. If you are looking to evade the complexities of web crawling, you can make use of our dedicated web scraping service.


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