Home Backend Development Python Tutorial What is a crawler and the basic process of a crawler

What is a crawler and the basic process of a crawler

Jun 04, 2019 pm 05:58 PM
python reptile

With the rapid development of the Internet, more and more data are flooding this era. Obtaining and processing data has become an essential part of our lives, and crawlers have emerged as the times require.

Many languages ​​​​can crawl, but crawlers based on python are more concise and convenient. Crawlers have also become an essential part of the python language.

This article explains what a crawler is and the basic process of a crawler. The next issue will further understand the basic process of a crawler, Request and Response.

What is a crawler and the basic process of a crawler

#What is a crawler?

Crawler is a web crawler, in English it is Web Spider. Translated, it means a spider crawling on the Internet. If the Internet is regarded as a big web, then a crawler is a spider crawling around on the big web. When it encounters the food it wants, it will grab it.

We enter a URL in the browser, hit Enter, and see the page information of the website. This is when the browser requests the website's server and obtains network resources. Then, the crawler is equivalent to simulating the browser to send a request and obtain the HTML code. HTML code usually contains tags and text information, and we extract the information we want from it.

Usually a crawler starts from a certain page of a website, crawls the content of this page, finds other link addresses in the web page, and then crawls from this address to the next page, so that it keeps crawling. Go down and grab information in batches. Then, we can see that a web crawler is a program that continuously crawls web pages and captures information.


The basic process of the crawler:

1. Initiate a request:

Initiate to the target site through the HTTP library Request, that is, send a Request. The request can contain additional headers and other information, and then wait for the server to respond. The process of this request is like opening the browser, entering the URL: www.baidu.com in the browser address bar, and then clicking Enter. This process is actually equivalent to the browser acting as a browsing client and sending a request to the server.

2. Get the response content:

If the server can respond normally, we will get a Response. The content of the Response is the content to be obtained. The type may include HTML, Json string, binary Data (pictures, videos, etc.) and other types. This process is that the server receives the client's request and parses the web page HTML file sent to the browser.

3. Parse the content:

The obtained content may be HTML, which can be parsed using regular expressions and web page parsing libraries. It may also be Json, which can be directly converted to Json object parsing. It may be binary data that can be saved or further processed. This step is equivalent to the browser getting the server-side file locally, interpreting it and displaying it.

4. Save data:

The saving method can be to save the data as text, save the data to the database, or save it as a specific jpg, mp4 and other format files. This is equivalent to downloading pictures or videos on the webpage when we browse the web.

The above is the detailed content of What is a crawler and the basic process of a crawler. For more information, please follow other related articles on the PHP Chinese website!

Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

PHP and Python: Different Paradigms Explained PHP and Python: Different Paradigms Explained Apr 18, 2025 am 12:26 AM

PHP is mainly procedural programming, but also supports object-oriented programming (OOP); Python supports a variety of paradigms, including OOP, functional and procedural programming. PHP is suitable for web development, and Python is suitable for a variety of applications such as data analysis and machine learning.

Choosing Between PHP and Python: A Guide Choosing Between PHP and Python: A Guide Apr 18, 2025 am 12:24 AM

PHP is suitable for web development and rapid prototyping, and Python is suitable for data science and machine learning. 1.PHP is used for dynamic web development, with simple syntax and suitable for rapid development. 2. Python has concise syntax, is suitable for multiple fields, and has a strong library ecosystem.

Python vs. JavaScript: The Learning Curve and Ease of Use Python vs. JavaScript: The Learning Curve and Ease of Use Apr 16, 2025 am 12:12 AM

Python is more suitable for beginners, with a smooth learning curve and concise syntax; JavaScript is suitable for front-end development, with a steep learning curve and flexible syntax. 1. Python syntax is intuitive and suitable for data science and back-end development. 2. JavaScript is flexible and widely used in front-end and server-side programming.

PHP and Python: A Deep Dive into Their History PHP and Python: A Deep Dive into Their History Apr 18, 2025 am 12:25 AM

PHP originated in 1994 and was developed by RasmusLerdorf. It was originally used to track website visitors and gradually evolved into a server-side scripting language and was widely used in web development. Python was developed by Guidovan Rossum in the late 1980s and was first released in 1991. It emphasizes code readability and simplicity, and is suitable for scientific computing, data analysis and other fields.

Can vs code run in Windows 8 Can vs code run in Windows 8 Apr 15, 2025 pm 07:24 PM

VS Code can run on Windows 8, but the experience may not be great. First make sure the system has been updated to the latest patch, then download the VS Code installation package that matches the system architecture and install it as prompted. After installation, be aware that some extensions may be incompatible with Windows 8 and need to look for alternative extensions or use newer Windows systems in a virtual machine. Install the necessary extensions to check whether they work properly. Although VS Code is feasible on Windows 8, it is recommended to upgrade to a newer Windows system for a better development experience and security.

Can visual studio code be used in python Can visual studio code be used in python Apr 15, 2025 pm 08:18 PM

VS Code can be used to write Python and provides many features that make it an ideal tool for developing Python applications. It allows users to: install Python extensions to get functions such as code completion, syntax highlighting, and debugging. Use the debugger to track code step by step, find and fix errors. Integrate Git for version control. Use code formatting tools to maintain code consistency. Use the Linting tool to spot potential problems ahead of time.

How to run python with notepad How to run python with notepad Apr 16, 2025 pm 07:33 PM

Running Python code in Notepad requires the Python executable and NppExec plug-in to be installed. After installing Python and adding PATH to it, configure the command "python" and the parameter "{CURRENT_DIRECTORY}{FILE_NAME}" in the NppExec plug-in to run Python code in Notepad through the shortcut key "F6".

Is the vscode extension malicious? Is the vscode extension malicious? Apr 15, 2025 pm 07:57 PM

VS Code extensions pose malicious risks, such as hiding malicious code, exploiting vulnerabilities, and masturbating as legitimate extensions. Methods to identify malicious extensions include: checking publishers, reading comments, checking code, and installing with caution. Security measures also include: security awareness, good habits, regular updates and antivirus software.

See all articles