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Web crawler framework of Python framework
1. Getting to know web crawlers for the first time
Web crawlers can automatically browse or grab information in the network according to specified rules (web crawler algorithms), and it is easy to write crawler programs or scripts through Python. Our common search engines are inseparable from web crawlers. The name of Baidu’s search engine crawler is Baidu Spider. It crawls massive amounts of Internet information every day, collects and organizes information such as web pages, pictures, and videos on the Internet. Then when the user enters the corresponding keywords in the Baidu search engine, Baidu will find relevant content from the collected network information, and then present the information to the user in a certain order. During the working process of Baidu Spider, the search engine will build a scheduler to schedule the work of Baidu Spider. These schedulers need to use certain algorithms to realize. Using different algorithms, the work efficiency of crawlers will be different, and the results of crawling will also be different. Therefore, when learning crawlers, it is necessary not only to understand the implementation process of crawlers, but also to understand some common crawler algorithms. Customize the corresponding algorithm.
Crawlers are generally divided into the following categories according to the technology and structure implemented: general web crawlers, focused web crawlers, incremental web crawlers, and deep web crawlers. In actual development, often