Chapter 11. Web Scraping: Acquiring and Storing Data from the Web

Web scraping is an essential part of data mining in today’s world, as you can find nearly everything on the Web. With web scraping, you can use Python libraries to explore web pages, search for information, and collect it for your reporting. Web scraping lets you crawl sites and find information not easily accessible without robotic assistance.

This technique gives you access to data not contained in an API or a file. Imagine a script to log into your email account, download files, run analysis, and send an aggregated report. Imagine testing your site to make sure it’s fully functional without ever touching a browser. Imagine grabbing data from a series of tables on a regularly updated website. These examples show how web scraping can assist with your data wrangling needs.

Depending on what you need to scrape—local or public websites, XML documents—you can use many of the same tools to accomplish these tasks. Most websites contain data in HTML code on the site. HTML is a markup language, and uses brackets (like our XML example in Chapter 3) to hold data. In this chapter, we will use libraries that understand how to parse and read markup languages like HTML and XML.

There are many sites that use internal APIs and embedded JavaScript to control the content on their pages. Because of these new ways to build the Web, not all of the information can be found using page-reading scrapers. We’ll also learn how to use some ...

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