What is a web crawler?

What is a web crawler? Web crawler, also called Web Spider, is a very vivid name. If the Internet is compared to a spider web, then Spider is a spider crawling around on the Internet. Strictly speaking, a web crawler is a program or script that automatically crawls information on the World Wide Web according to certain rules.

As we all know, the traditional web crawler is an important functional module in the upstream of search engine, and it is the first level responsible for the core function of content indexing of search engine.

However, with the advent of the era of big data and the explosion of information, the data on the Internet has shown a doubling trend. How to efficiently obtain the interesting content on the Internet and make use of it is an important value-added direction in the field of data mining. It is for this purpose that web crawler has ushered in a new wave of revival and become a hot technology that has developed rapidly in recent years.

At present, web crawler can be divided into four development stages:

The first stage was the early crawler, when the Internet was basically completely open and the flow of people was the mainstream.

The second stage is distributed crawler, and the amount of Internet data is increasing, so there is a scheduling problem for crawler.

The third stage is the dark reptile. At this time, there are new services on the Internet, and there is little connection between the data of these services, such as Taobao's evaluation.

The fourth stage is intelligent crawler, which mainly crawls social network data and solves problems such as account number, network closure, anti-crawling means and blocking methods.

At present, the main application fields of web crawler are search engine, data analysis, information aggregation, financial investment analysis and so on.

You cannot make a silk purse out of a sow's ear. In these application fields, even the best algorithms and models can't get results if there is no web crawler to grab data for them. Moreover, without the data of machine learning modeling, it is impossible to form a model that can solve practical problems. Therefore, in the hot field of artificial intelligence, web crawler is playing an increasingly critical role as a data producer. Without web crawler, data mining and artificial intelligence will become passive water and trees without roots.

Specifically, the case of crawler's popular application field now is the application of price comparison website. At present, in order to attract users, all major e-commerce platforms have launched various discount activities. The same product may have different prices on different online shopping platforms, which gives birth to price comparison websites or apps, such as rebate networks and discount networks. These price comparison websites use a web crawler to monitor the price fluctuations of major e-commerce companies in real time. Is to collect prices, models, configurations, etc. Goods, and then do processing, analysis and feedback. In this way, you can get the information about whether a product on an e-commerce website has a discount in a few seconds.

Regarding the problem of web crawler, you can look at the video tutorial on this page, Python crawler+voice library. After reading it, you will have a clear understanding of web crawler.