In simple words, web scraping is the process of extracting desired data from a web resource. This method involves different procedures such as interacting with the web resource, choosing the appropriate data, obtaining information from the data, and converting the data to the desired format. With all the previous methods considered, a major spotlight will be thrown on the process of pulling the required data from the semistructured data.
Scraping a web resource is not always welcomed by the owners. Some companies put a restriction on using bots against them. It's etiquette to follow certain rules while scraping. The following are the dos and don'ts of web scraping:
- Do refer to the terms and conditions: The first thing that should come to our mind before we begin scraping is terms and conditions. Do visit the website's terms and conditions page and get to know whether they prohibit scraping from their site. If so, it's better to back off.
- Don't bombard the server with a lot of requests: Every website runs on a server that can serve only a specific amount of workload. It is equivalent to being rude if we bombard the server with lots of requests in a specific span of time, which may result in sever breakdown. Wait for some time between requests instead of bombarding the server with too many requests at once.
- Do track the web resource from time to time: A website doesn't always stay the same. According to its usability and the requirement of users, they tend to change from time to time. If any alteration has taken place in the website, our code to scrape may fail. Do remember to track the changes made to the site, modify the scrapper script, and scrape accordingly.
Generally, the process of web scraping requires the use of different tools and libraries such as the following:
- Chrome DevTools or FireBug Add-on: This can be used to pinpoint the pieces of information in an HTML/XML page.
- HTTP libraries: These can be used to interact with the server and to pull a response document. An example of this is
python-requests. - Web scraping tools: These are used to pull data from a semistructured document. Examples include
BeautifulSouporScrappy.
The overall picture of web scraping can be observed in the following steps:
- Identify the URL(s) of the web resource to perform the web scraping task.
- Use your favorite HTTP client/library to pull the semistructured document.
- Before extracting the desired data, discover the pieces of data that are in semistructured format.
- Utilize a web scraping tool to parse the acquired semistructured document into a more structured one.
- Draw the desired data that we are hoping to use. That's all, we are done!