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

As a programming language, Python is a pure free software, which is deeply loved by programmers because of its concise and clear syntax and the characteristics of forcing the use of blank characters for sentence indentation. Accomplish a task in different programming languages: C needs to write 1000 lines of code; java needs to write 100 lines of code; python only needs to write 20 lines of code. If you use python to complete programming tasks, write less code, the code is concise and short and more readable, a team will write code faster when developing, and high development efficiency makes the work more efficient.

Python is very suitable for developing the programming language of web crawler. Compared with other static programming languages, the interface of Python to grab web documents is more concise. Compared with other dynamic scripting languages, Python's urllib2 package provides a more complete API for accessing web documents. There are excellent third-party packages in python that can efficiently crawl web pages and complete the tag filtering function of web pages with very short code.

The architecture of the python crawler:

Crawler frame

1. URL manager: manages the url collection to be crawled and the crawled url collection, and transmits the url to be crawled to the web downloader

2. Web page downloader: crawl the web page corresponding to url, store it as a string, and send it to the web page parser

3. Web page parser: parse out valuable data, store it, and supplement url to URL manager.

The workflow of python is:

Through the URL manager, the Python crawler determines whether to climb the URL, if it needs to climb the URL, passes it to the downloader through the scheduler, downloads the URL content, and transmits it to the parser through the scheduler, parses the URL content, and passes the value data and the new URL list to the application through the scheduler, and outputs the value information.

Python is a programming language very suitable for the development of web crawlers, providing modules such as urllib, re, json, pyquery, etc., while there are many shaping frameworks, such as Scrapy framework, PySpider crawler system, etc., the code is very simple and convenient, and it is the preferred programming language for beginners to learn web crawlers. Crawlers refer to the crawling of network resources, because of the script characteristics of python, python is easy to configure, and the processing of characters is also very flexible. In addition, python has a wealth of network crawling modules, so the two are often linked together, and python is more suitable for beginners to learn.

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