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Explaining how data scraping works

Web scraping is a term that you may have heard a million times before, but that probably does not mean anything to you. Web scraping can be defined as a technique that is used in order to extract data from websites and saving it into a database. The process is very much similar to web indexing, the only difference being the motivation behind the process. The information that is displayed by the vast majority of online pages can be easily viewed as long as you have a web browser. But is scraping data from websites actually necessary? For some companies the information resulting from data mining is essential for market research and even for detecting theft. So are you curious to learn how information gets on web browsers and how it is retrieved?

Explaining how data scraping works

Interacting with a website

Instead of beginning with complicated explanations, it is important to clear up what happens when a user visits a website. When you interact with an online platform, meaning if you click on a link or type into the search engine field, actually triggers an event. This means that the site interprets the JavaScript code. In order to provide you with the next page, the browser makes calculations and works beyond just providing the page requested. This process is typically referred to as client-side processing. To put it in other words, in addition to sending you the text and image that you want, the website sends files that contain certain codes which inform the browser of the event that are occurring.

The anatomy of the online page

A HTML page is generally structured as a hierarchy of boxes, boxes that contain smaller ones. These boxes or tags perform a number of functions, like producing tables, links or images. In addition to this, tags can be unique identifiers or they can be part of groups that are called “classes”. All of this makes it possible to capture individual elements within a document and selecting the right elements is the key to writing a scraper. Nonetheless, there are different types of elements present in an HTML document, reason why programmers have to become familiar with all of them to do their job.

What we scrapers do

The job of the web scraper is to observe the page and of course its source code. The purpose of the operation is to detect the patterns in the HTML and to extract the information. Basically, programmers manually copy the data from the sites in a matter of seconds. In order to retrieve the information, IT experts can resort to a couple of techniques. Firstly, they will get the info from the web-based APIs, which means interfaces that are provided either by online databases or modern applications such as Twitter or Facebook. Another powerful method that is used is screen scraping. During this process, the programmer extracts the structured content of a normal page with the help of software or by simply writing small pieces of code. The whole purpose of these methods is to access machine-readable data, meaning that which is created for computers and not human users. Classic formats include CSV, XML and Excel.