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Python Web Scraping

Python Web Scraping

By : Jarmul
3 (2)
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Python Web Scraping

Python Web Scraping

3 (2)
By: Jarmul

Overview of this book

The Internet contains the most useful set of data ever assembled, most of which is publicly accessible for free. However, this data is not easily usable. It is embedded within the structure and style of websites and needs to be carefully extracted. Web scraping is becoming increasingly useful as a means to gather and make sense of the wealth of information available online. This book is the ultimate guide to using the latest features of Python 3.x to scrape data from websites. In the early chapters, you'll see how to extract data from static web pages. You'll learn to use caching with databases and files to save time and manage the load on servers. After covering the basics, you'll get hands-on practice building a more sophisticated crawler using browsers, crawlers, and concurrent scrapers. You'll determine when and how to scrape data from a JavaScript-dependent website using PyQt and Selenium. You'll get a better understanding of how to submit forms on complex websites protected by CAPTCHA. You'll find out how to automate these actions with Python packages such as mechanize. You'll also learn how to create class-based scrapers with Scrapy libraries and implement your learning on real websites. By the end of the book, you will have explored testing websites with scrapers, remote scraping, best practices, working with images, and many other relevant topics.
Table of Contents (10 chapters)
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One million web pages

To test the performance of concurrent downloading, it would be preferable to have a larger target website. For this reason, we will use the Alexa list, which tracks the top one million most popular websites according to users who have installed the Alexa Toolbar. Only a small percentage of people use this browser plugin, so the data is not authoritative, but it's fine for our purposes and gives us a larger list to crawl.

These top one million web pages can be browsed on the Alexa website at http://www.alexa.com/topsites. Additionally, a compressed spreadsheet of this list is available at http://s3.amazonaws.com/alexa-static/top-1m.csv.zip, so scraping Alexa is not necessary.

Parsing the Alexa list

The Alexa list is provided in a spreadsheet...

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