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This article mainly explains "what tools Python crawler uses", interested friends may wish to take a look. The method introduced in this paper is simple, fast and practical. Let's let Xiaobian take you to learn "what tools Python crawler uses"!

Is it necessary to learn reptiles?

I think it's a question that doesn't need discussing.

Crawlers,"useful" and "interesting"!

In this era when data is king, we want to get the data we need from this huge Internet, and crawler is the best choice. Whether it is the past "search engine" or the current popular "data analysis," it is an essential means of obtaining data. After mastering reptiles, you see a lot of "interesting" things! No matter what your technical orientation, mastering this technology will allow you to explore the thriving Internet and collect all kinds of data or documents easily and quickly. In addition to fun and interesting, crawlers are really very useful. In fact, many companies have requirements for crawlers when recruiting.

So to learn web crawler, you need to master some basic knowledge:

Python basics commonly used in web crawlers

HTTP protocol communication principle (what is a process when we browse the web, how is it composed?)

HTML, CSS, JS Basics (Mastering Web page structure and locating specific elements from Web pages)

With these basics in place, you can start learning how to crawl. Now learn reptiles, of course Python reptiles, this is the absolute mainstream of the moment.

However, many of his friends would still have doubts!

Should I learn Python first?

How do I advance after learning the basics?

What's the use of learning crawler?

Pyhton has surpassed Java to become number one on the latest programming language rankings, with more and more programmers choosing Python, and some even saying that using Python is "programming for the future." As for the relationship between Python and "crawler," of course, you need to master some basic knowledge of Python before learning crawler.

But if you're just starting Python and want to go deeper, then once you've mastered the basics of Python, I recommend that you start with crawlers rather than anything else.

First of all, it is really easy to master a lot of knowledge in Python Basic Learning Tutorial by learning crawler. Of course, this may also be because the Python world has produced many excellent crawler projects, which makes Python leave this impression on everyone, but there is no doubt that crawlers can train and improve your Python skills.

Second, after mastering crawler technology, you will see a lot of different landscapes. You'll have fun crawling through your data, and believe me, this fun and curiosity will give you an innate fondness for Python, so you'll have the motivation to learn Python in depth.

We use Python to develop crawlers, and Python's greatest strength lies not in the language itself but in its large and active developer community and billions of third-party toolkits. With these toolkits we can quickly implement one function after another without having to build our own wheels. The more toolkits we have, the easier it is for us to write crawler programs. In addition, the target of crawler work is "Internet," so HTTP communication and HTML, CSS, JS these skills will be used when writing crawler programs.

As developers, code is the best teacher, learning in practice, speaking directly from code, is the way we programmers learn. As long as you have Python basics, this column is enough to take you from completely ignorant of crawlers to the ability to actually develop crawlers and use crawlers at work.

In actual production, the data we need generally cannot escape such a page structure:

News Feed Crawler--Crawl RSS Feed Data

Netease News Crawler--Pan-Crawl Technology

Netease crawler optimization--large-scale data processing technology

Douban Reading Crawler--Test-driven Design and Advanced Anti-crawling Technology Practice

Mushroom Street Collection--Processing Deep Inheritance javascript Website

Application example of slow crawler--Zhihu crawler

Later I will take you to realize these page structures one by one, realize page crawlers with different technologies, let everyone understand what kind of technology can be used to deal with under what circumstances through specific code practice, encounter anti-crawling measures How to solve, through specific applications to establish specific knowledge of crawlers in understanding the technical theory behind.

Speaking of which, some partners may have to ask: after writing the crawler program? Don't worry, after writing the crawler program, I will take you to deploy our crawler program, and really let our crawler "show its ambition."

Master Scrapy Framework Development

Learn Pan-crawling Technology to Deal with Mass Data

Optimize your incremental crawlers

Solve large-scale concurrent crawler projects through distributed crawlers

Docker container technology for crawler deployment

How much data is hidden on the internet? What difference does it make to our lives and work? Keep your curiosity, from now on, let's learn reptiles together, play reptiles together, use reptiles together!

Let's talk about Python crawler tools we want to use! This is also the first step in learning reptiles!

What's the first step for a reptile?

Yes, it must be the target site analysis!

1.Chrome

Chrome is the most basic tool for crawlers. Generally, we use it to do initial crawling analysis, page logic jump, simple js debugging, network request steps, etc. Most of our early work was done on it, and without Chrome, to put it mildly, we'd be going backwards hundreds of years from modern times!

Similar tools: Firefox, Safari, Opera

2.Charles

Charles corresponds to Chrome, but it is used to do App-side network analysis, compared to the web side, App-side network analysis is relatively simple, focusing on analyzing the parameters of each network request. Of course, if the other party has done parameter encryption on the server side, it involves knowledge of reverse engineering, and that piece is a large basket of tools. Let's not talk about it here.

Similar tools: Fiddler, Wireshark, Anyproxy

Next, analyze the site's anti-crawler

3.cUrl

Wikipedia describes it this way.

cURL is a file transfer tool that works on the command line using URL syntax, first released in 1997. It supports file upload and download, so it is a comprehensive transmission tool, but according to tradition, it is customary to call cURL a download tool. cURL also contains libcurl for program development.

When doing crawler analysis, we often have to simulate the request. At this time, if you write a piece of code, it is too much fuss. Copy a cURL directly through Chrome and run it on the command line to see the results. The steps are as follows.

4.Postman

Of course, most websites are not where you copy the cURL link and change the parameters to get the data. Next, we need to use Postman's "killer" for deeper analysis. Why the "killer"? Because it's really powerful. With cURL, we can transplant the requested content directly, and then modify the request, check the content parameters we want, very elegant

5.Online JavaScript Beautifier

With the above tools, you can basically solve most of the site, is a qualified junior crawler engineer. At this time, we want to advance to face more complex website crawlers, this stage, you not only have to know the back-end knowledge, but also need to understand some front-end knowledge, because many website anti-crawling measures are placed on the front-end. You need to extract the js information of the other site, and need to understand and reverse back, native js code is generally not easy to read, then, it is necessary to help you format it

6.EditThisCookie

Crawlers and anti-crawlers are a tug of war without smoke, and you never know what holes the other party will bury for you, such as tampering with Cookies. At this time you need it to assist you in your analysis. After installing EditThisCookie plug-in through Chrome, we can click on the small icon in the upper right corner and then add, delete and check the information in Cookies, greatly improving the simulation of Cookies information.

Next, design the crawler architecture

7.Sketch

We shouldn't rush to write about crawlers when we're sure we can crawl. Instead, we should start designing the structure of the reptile. According to the needs of the business, we can do a simple crawling analysis, which will help us to develop efficiency later. The so-called sharpening does not miss the firewood work. For example, you can consider, is it search crawling or traversal crawling? BFS or DFS? How many concurrent requests are there? After considering these questions, we can draw a simple architecture diagram through Sketch.

Similar tools: Illustrator, Photoshop

Finally began a pleasant reptile development journey

Finally to carry out the development, after the above steps, we to this step, is already ready for everything but the east wind. At this time, we only need to do code and data extraction.

8.XPath Helper

When extracting web page data, we generally need to use xpath syntax to extract page data information, generally, but we can only write the syntax, send a request to the other party's web page, and then print it out to know whether the data we extracted is correct. This will initiate a lot of unnecessary requests on the one hand, and waste our time on the other. This can use XPath Helper, after installing the plugin through Chrome, we only need to click it to write the syntax in the corresponding xpath, and then we can intuitively see our results on the right, efficiency up +10086

9.JSONView

We sometimes extract data in Json format because it is easy to use, and more and more websites tend to transmit data in Json format. At this time, after we install this plugin, we can easily view Json data.

10.JSON Editor Online

JSONView is the data returned directly on the web page. The result is Json, but most of the time the result we request is HTML page data rendered by the front end. The json data we get after initiating the request cannot be displayed well in the terminal. How to do? JSON Editor Online can help you format your data well, format it in one second, and realize the intimate folding Json data function.

Now that I have seen this, I believe you are also very studious friends. Here is an egg tool for you.

0.ScreenFloat

What does it do? In fact, it is a screen floating tool, in fact, do not underestimate it, it is particularly important, when we need to analyze parameters, often need to switch back and forth in several interfaces, this time there are some parameters, we need to compare their differences, this time, you can float through it first, do not have to switch in several interfaces. Very convenient. Give you a hidden play, such as the above picture.

At this point, I believe that everyone has a deeper understanding of "what tools Python crawlers use", so let's actually operate it! Here is the website, more related content can enter the relevant channels for inquiry, pay attention to us, continue to learn!

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