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This article mainly introduces "what are Python crawler-related tools". In daily operation, I believe many people have doubts about what problems Python crawler-related tools have. Xiaobian consulted all kinds of materials and sorted out simple and easy operation methods. I hope to help you answer the doubts about "what are Python crawler-related tools"! Next, please follow the small series to learn together!

Web crawlers and related tools

The concept of web crawler

Web crawler, formerly known as spider, is a robot program (or script) that automatically browses the World Wide Web and obtains information according to certain rules. It has been widely used in Internet search engines. As anyone who has used the Internet and browsers knows, Web pages contain hyperlinks in addition to text messages for users to read. Web crawler system is through the hyperlink information in the web page to continuously obtain other pages on the network. Because of this, the process of network data collection is like a crawler or spider roaming on the network, so it is called a web crawler or web spider.

Application areas of crawler

In an ideal state, all ICP (Internet Content Provider) should provide API interfaces for their own websites to share the data they allow other programs to obtain. In this case, crawlers are not necessary. Domestic famous e-commerce platforms (such as Taobao, Jingdong, etc.), social platforms (such as Tencent Weibo, etc.) and other websites provide their own Open APIs, but such Open APIs usually limit the data that can be crawled and the frequency of crawling data. For most companies, timely access to industry-related data is one of the important aspects of enterprise survival. However, most enterprises lack industry data because of their inherent shortcomings. It is very important to use crawlers to obtain data reasonably and extract commercially valuable information from it. Of course, crawlers have many important application areas, some of which are listed below:

search engine

news aggregation

social application

public opinion monitoring

industry data

Legality and background research

Discussion on the Legality of Crawlers

The field of web crawlers is still in the pioneering stage. Although the Internet world has established certain ethical norms through its own rules of the game (Robots Protocol, full name is "web crawler exclusion standard"), the legal part is still being established and perfected, that is to say, this field is still a gray area for the time being.

"If the law does not prohibit it, it is permission." If the crawler obtains the data displayed at the front end (public information on the webpage) rather than the private sensitive information in the background of the website like a browser, it will not worry too much about the restriction of laws and regulations, because the development speed of the big data industry chain far exceeds the perfection of the law.

When crawling websites, you need to restrict your crawlers from complying with the Robots protocol, and at the same time control the speed at which web crawlers grab data; when using data, you must respect the intellectual property rights of the website (since the Web 2.0 era, although a lot of data on the Web is provided by users, the website platform has invested in operating costs, and when users register and publish content, the platform usually has acquired ownership, use, and distribution rights to the data). If these rules are violated, the chances of losing a lawsuit are quite high.

Robots.txt file

Most websites define robots.txt files. Take Taobao's robots.txt file as an example to see what restrictions the website has on crawlers.

User-agent: BaiduspiderAllow: /articleAllow: /oshtmlDisallow: /product/Disallow: /User-Agent: GooglebotAllow: /articleAllow: /oshtmlAllow: /productAllow: /spuAllow: /dianpuAllow: /overseaAllow: /listDisallow: /User-agent: BingbotAllow: /articleAllow: /oshtmlAllow: /productAllow: /spuAllow: /dianpuAllow: /overseaAllow: /listDisallow: /User-Agent: 360SpiderAllow: /articleAllow: /oshtmlDisallow: /User-Agent: YisouspiderAllow: /articleAllow: /oshtmlDisallow: /User-Agent: SogouspiderAllow: /articleAllow: /oshtmlAllow: /productDisallow: /User-Agent: Yahoo! SlurpAllow: /productAllow: /spuAllow: /dianpuAllow: /overseaAllow: /listDisallow: /User-Agent: *Disallow: /

Note the last line of the first paragraph of robots.txt above, by setting "Disallow: /" prohibit Baidu crawler access to all pages except the "Allow" specified page. Therefore, when you search for "Taobao" in Baidu, the search results will appear below: "Due to the existence of restrictions on the robots.txt file of this website (restricted search engine crawling), the system cannot provide the content description of this page." Baidu as a search engine, at least on the surface to comply with Taobao's robots.txt protocol, so users can not search from Baidu to Taobao internal product information.

At this point, the study of "What are Python crawler-related tools" is over, hoping to solve everyone's doubts. Theory and practice can better match to help everyone learn, go and try it! If you want to continue learning more relevant knowledge, please continue to pay attention to the website, Xiaobian will continue to strive to bring more practical articles for everyone!

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