What does Python have to do with crawlers? Why is Python called a crawler?

Crawler generally refers to the crawling of network resources. Due to the scripting characteristics of Python, it is easy to configure and process characters very flexibly. Python has rich network crawling modules, so the two are often linked together and Python is called a crawler. Crawlers can crawl the content of a website or an application to extract useful valuable information. It can also simulate the user’s operation behavior on the browser or app application to realize program automation.

Why is Python called a crawler?

As a programming language, Python is pure free software, and is deeply loved by programmers for its concise and clear syntax and mandatory use of whitespace for statement indentation. Use different programming languages ​​to complete a task: C language needs to write a total of 1000 lines of code; Java needs to write 100 lines of code; Python only needs to write 20 lines of code. If Python is used to complete programming tasks, the amount of code written is small, the code is concise, short, and highly readable. When a team is developing, the code writing efficiency will be faster, and the high development efficiency will make the work more efficient.

Python is a very suitable programming language for developing web crawlers. Compared with other static programming languages, Python has a simple interface for crawling web documents. Compared with other dynamic scripting languages, Python’s urllib2 package provides a more complete API for accessing web documents. Some third-party packages in Python can implement web crawling, and can complete the tag filtering function of web pages with very short codes.

The structure of the Python crawler consists of:

Architecture composition of Python crawler

crawler framework

1. URL manager: manages the url set to be crawled and the url set that has been crawled, and sends the url to be crawled to the web page downloader;

2. Web page downloader: crawl the web page corresponding to the 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 add url to the URL manager at the same time.

Workflow in Python:

Workflow in Python

The Python crawler uses the URL manager to determine whether there is a URL to be crawled. If there is a URL to be crawled, it is passed to the downloader through the scheduler, downloads the URL content, and transmits it to the parser through the scheduler. The process of passing the list of URLs to the application through the dispatcher and outputting the value information.

Python is a programming language that is very suitable for developing web crawlers. It provides modules such as urllib, re, json, and pyquery, as well as many forming frameworks, such as Scrapy framework and PySpider crawler system. The code is very concise and convenient, and it is the programming language of choice for beginners to learn web crawlers. Crawler refers to the crawling of network resources. Because of the scripting 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. The Python language is suitable for novices. study.

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