Ohh fancy, web crawling. What is it? Web crawlers scrape data from a website. Most websites are full of data, for example, BBC News website has news article data. This can be grabbed by a web crawler and displayed on your own website. Web crawlers typically follow all links on the page, so lots of data can be grabbed without any manual copy and pasting.
Crawlers work by firstly making a request to the website it is trying to crawl, then the HTML is parsed and searched for link tags. These are stored and looped through by the crawler. The idea is that all the links on a website get crawled by the crawler. Once the links have been established, we can grab text from a given HTML page, we can also target CSS selectors. Most websites use different semantic HTML elements and CSS selectors to store different parts of data on a website.
For example, headings may be stored under the heading semantic HTML element, when we crawl the website we can target just the heading tag and grabbing and storing the test stored within it.
Another advantage to web scraping is, it has a very low learning curve. This is because there are so many libraries that have been creating in multiple programming languages which make web scraping a breeze. This also makes web scraping inexpensive as it doesn’t require extensive training to grab entire data sets of a website.
Difficult to analyse – For anybody who is not an expert, the scraping processes are confusing to understand. Although this is not a major problem, some errors could be fixed faster if it was easier to understand for more software developers.
Data analysis – The data that has been extracted will first need to be treated so that they can be easily understood. In certain cases, this might take a long time and a lot of energy to complete.
Time – It is common for new data extraction applications to take some time in the beginning of the software often has a learning curve. Sometimes web scraping services take time to become familiar with the core application and need to adjust to the scrapping language. This means that such services can take some days before they are up and running at full speed.
Speed and protection policies – Most web scrapping services are slower than API calls and another problem is the websites that do not allow screen scrapping. In such cases, web scrapping services are rendered useless. Also, if the developer of the website decides to introduce some changes in the code, the scrapping service might stop working.
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