Book Image

Python Web Scraping - Second Edition

By : Katharine Jarmul
Book Image

Python Web Scraping - Second Edition

By: Katharine 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.

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Table of Contents (10 chapters)
Preface
Preface
What this book covers
What you need for this book
Who this book is for
Conventions
Reader feedback
Customer support
Free Chapter
1
Introduction to Web Scraping
Introduction to Web Scraping
When is web scraping useful?
Is web scraping legal?
Python 3
Background research
Crawling your first website
Summary
2
Scraping the Data
Scraping the Data
Analyzing a web page
Three approaches to scrape a web page
CSS selectors and your Browser Console
XPath Selectors
LXML and Family Trees
Comparing performance
Scraping results
Summary
3
Caching Downloads
Caching Downloads
When to use caching?
Adding cache support to the link crawler
Disk Cache
Key-value storage cache
Summary
4
Concurrent Downloading
Concurrent Downloading
One million web pages
Sequential crawler
Threaded crawler
How threads and processes work
Performance
Summary
5
Dynamic Content
Dynamic Content
An example dynamic web page
Reverse engineering a dynamic web page
Rendering a dynamic web page
The Render class
Summary
6
Interacting with Forms
Interacting with Forms
The Login form
Extending the login script to update content
Automating forms with Selenium
Summary
7
Solving CAPTCHA
Solving CAPTCHA
Registering an account
Optical character recognition
Solving complex CAPTCHAs
Using a CAPTCHA solving service
CAPTCHAs and machine learning
Summary
8
Scrapy
Scrapy
Installing Scrapy
Starting a project
Different Spider Types
Scraping with the shell command
Visual scraping with Portia
Automated scraping with Scrapely
Summary
9
Putting It All Together
Putting It All Together
Google search engine
Facebook
Gap
BMW
Summary

Different Spider Types

In this Scrapy example, we have utilized the Scrapy CrawlSpider, which is particularly useful when crawling a website or series of websites. Scrapy has several other spiders you may want to use depending on the site and your extraction needs. These spiders fall under the following categories:

  • Spider: A normal scraping spider. This is usually used for just scraping one type of page.
  • CrawlSpider: A crawl spider; usually used for traversing a domain and scraping one (or several) types of pages from the pages it finds by crawling links.
  • XMLFeedSpider: A spider which traverses an XML feed and extracts content from each node.
  • CSVFeedSpider: Similar to the XML spider, but instead can parse CSV rows within the feed.
  • SitemapSpider: A spider which can crawl a site with differing rules by first parsing the Sitemap.

Each of these spiders are included in your default Scrapy installation, so you can access...

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