Shulou(Shulou.com)06/03 Report--

This article mainly introduces the crawler how to crawl data, has a certain reference value, interested friends can refer to, I hope you can learn a lot after reading this article, let the editor take you to understand it.

In data analysis, first of all, there must be a large amount of data, usually using crawlers to collect peer information for analysis, mining useful data. But there are many such materials, which only rely on manual collection, which takes a long time, and there is also a lazy way to crawl data with crawlers. How does the crawler realize data collection? The essence of Web crawler is a http request, the browser is the user to take the initiative to operate, and then complete the HTTP request, crawler needs a complete architecture to complete, crawler needs a complete architecture to complete.

1. Website management.

At the beginning, urlManager adds a new url to the background collection, determines whether the url to be added is in the container or the url to be crawled, then gets the url to be crawled, and moves the url from the crawled url collection to the crawled url collection.

2. Download the web page.

The downloader passes the received url to the Internet, which returns the html file to the downloader, and the downloader saves it locally, usually for distributed deployment, one as a submission and the other as a request agent.

3, extract the content, the main task of the page parser is to obtain valuable data from the html web page string and a new url list.

The commonly used data extraction methods are css selector, regex and xpath rule extraction. Usually, after the extraction is completed, the data should be cleaned or customized, so that the requested unstructured data can be converted into the desired structured data.

4. Keep the data.

The data is stored in relevant databases, queues, files, etc., which is convenient for data calculation and docking with applications.

How does the crawler collect data? As can be seen from the above introduction, a complete crawler life cycle includes: URL management, web page download, content extraction, preservation.

Many crawls will affect the other side's server, so the other side will take anti-crawler measures, such as IP restrictions, CAPTCHA detection and so on. In order to successfully complete the data collection task, we also need in-depth research on how to break through the anti-crawler mechanism. At the same time, we should also reduce the speed of collection, abide by the reptile agreement, and act in accordance with the law!

Thank you for reading this article carefully. I hope the article "how to crawl data by a crawler" shared by the editor will be helpful to everyone. At the same time, I also hope that you will support and pay attention to the industry information channel. More related knowledge is waiting for you to learn!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.