Web scraping refers to the process of extracting data from websites. It involves using various techniques to gather content from web pages that can be processed and analyzed. The data extracted can range from text, images, links, tables, and other content available on websites.

Key Concepts in Web Scraping:

  1. HTML Parsing: Web pages are typically structured using HTML, and scraping involves navigating this HTML structure to extract relevant information.
  2. Web Crawling: Involves visiting multiple web pages to collect data from across a site or even multiple sites.
  3. Selectors: Scraping typically uses CSS selectors, XPath, or regular expressions to locate specific elements in the HTML.

Common Tools & Libraries for Web Scraping:

  1. BeautifulSoup (Python): A library that simplifies parsing and extracting data from HTML and XML documents.
  2. Selenium: Used for automating web browsers to scrape data from dynamic websites (sites where content is generated by JavaScript).
  3. Scrapy: A powerful framework for large-scale web scraping that allows for complex crawling and extraction tasks.
  4. Requests (Python): A library to make HTTP requests and retrieve raw HTML content.
  5. Puppeteer (Node.js): A headless browser automation library for scraping dynamic content.

How Web Scraping Works:

  1. Sending a Request: The process starts by sending an HTTP request to the website’s server to retrieve the HTML content of a webpage.
  2. Parsing the Response: The HTML response is then parsed using a library like BeautifulSoup or lxml to locate specific pieces of data (e.g., titles, links, tables).
  3. Extracting Data: The required information is extracted, stored, and possibly cleaned for analysis.
  4. Storing Data: The extracted data can be saved to a file, database, or further processed.

Legal & Ethical Considerations:

  1. Website Terms of Service: It’s important to check if a website’s terms of service allow scraping. Some websites prohibit scraping or have specific rules about it.
  2. Robots.txt: A file that websites use to communicate which parts of their site are open or closed to web crawlers.
  3. Rate Limiting: Scraping too quickly or excessively can overwhelm a website’s server, so it’s best to respect rate limits.