Introduction to reptiles

introduce

Before, in the course of teaching , Many students have asked me such a question : Why study reptiles , What benefits can learning crawler bring to our future development ? In fact, the reasons for learning reptiles and the benefits for our future development are obvious , No matter from the practical application or from the employment .

We all know , We are in the era of big data , In the age of big data , To do data analysis , First of all, there must be data sources , And learning reptiles , We can get more data sources , And these data sources can be collected according to our purpose .

Youku's Mars intelligence agency is based on web crawlers and data analysis . The topic of each program is crawling the relevant data from the relevant popular interactive platform , And then the crawled data is obtained by data analysis . On the other hand , Youku is based on the progress of users watching videos in real time , Backward behavior data , Can speculate and calculate the audience's interest and hobbies , This is helpful to the editing of the program and the later programming .

Today's headline is an application of news recommendation , Its internal news data are crawled through the crawler program in each news website , And then push the news topics that users are interested in to their mobile phones through the corresponding processing and calculation .

In terms of employment , Reptile engineers are in short supply at present , And the salary is generally higher, so , Master this technology at a deeper level , For employment , It's very advantageous . Some people may learn to crawl for employment or job hopping . From this perspective , Crawler engineer is one of the good choices . With the advent of big data era , Crawler technology will be used more and more widely , There will be better development space in the future .

Today's summary

  • About reptiles
  • Reptile classification
  • robots agreement
  • Anti climbing mechanism
  • Anti climbing mechanism

Today's details

  • What is a reptile

    A crawler is a program that simulates surfing the web in a browser , Then let it go to the Internet to grab the process of data .

  • Which languages can implement crawler

       1.php: You can do crawlers .php Known as the most beautiful language in the world ( Of course, it's its own claim , It means that Wang Po sells melons ), however php In the implementation of crawler support multithreading and multi process aspects do not do well .

      2.java: You can do crawlers .java Can be very good processing and implementation of crawler , It's the only one that can work with python Go hand in hand and be python The number one enemy of . however java The implementation of crawler code is cumbersome , Restructuring costs a lot .

    3.c、c++: You can do crawlers . But it's just someone who's doing it this way ( bosses ) The embodiment of ability , It's not a wise and reasonable choice .

     4.python: You can do crawlers .python The implementation and processing of crawler syntax is simple , Beautiful code , There are many modules supported , The cost of learning is low , With a very powerful framework (scrapy etc. ) And it's hard to say ! No, but !

  • Classification of reptiles

      1. Universal crawler : General crawler is a search engine (Baidu、Google、Yahoo etc. )“ Grab system ” An important part of . The main purpose is to download web pages on the Internet to local , Form a mirror backup of Internet content .  In short, as much as possible ; Download all the web pages on the Internet , Put it on the local server to form a backup , In the relevant processing of these pages ( Extract key 、 Remove ads ), Finally, a user retrieval interface is provided .

    • How search engines capture website data on the Internet ?

      • The portal actively provides the search engine company with the information of its website url
      • Search engine companies and DNS Service provider cooperation , Get the website's url
      • The portal website is actively attached to the links of some well-known websites

2. Focus on reptiles : A focused crawler crawls the specified data on the network according to the specified requirements . for example : Get the title and review of the movie on douban , Instead of getting all the data values in the entire page .

  •  robots.txt agreement

    - If you don't want the crawler to crawl the data in the specified page of your portal , Then you can write a robots.txt To restrict the crawler's data crawling .robots The format of the protocol can be observed on Taobao robots( visit www.taobao.com/robots.txt that will do ). But here's the thing , The agreement is just the equivalent of an oral agreement , There is no use of technology to enforce regulation , So the agreement is to prevent the gentleman from the villain . But the crawler program we wrote in the learning crawler stage can be ignored first robots agreement .

  • The crawler

    - Portal through the corresponding strategy and technical means , Prevent crawlers from crawling the website data .

  • Reflect the crawler

    -  Crawler program through the corresponding strategy and technical means , Crack the portal's anti-crawler method , To crawl to the corresponding data .

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