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How to learn Python crawler technology efficiently? Many novices are not very clear about this. In order to help you solve this problem, the following editor will explain it in detail. People with this need can come and learn. I hope you can gain something.

Most Python crawlers crawl according to the process of "send request-get page-parse page-extract and store content" to simulate the process that people use browsers to get web information.

Steps to learn Python crawler techniques efficiently:

1. Learn the basic knowledge of Python web crawler

When learning Python web crawler, we should first understand the basic knowledge of Python, such as variables, strings, lists, dictionaries, tuples, manipulating sentences, grammar, etc., and lay a solid foundation to know what knowledge points are used when doing cases. In addition, you also need to understand the basic principles of network requests, web page structure, and so on.

2. Watch Python web crawler video tutorial to learn.

Watch the video or find a professional web crawler book "write Web crawler with Python", follow the video to learn the crawler code, tap more code, understand each line of code and start to practice, learning while doing can learn faster. Many people have misunderstandings, feel that they will not want to practice, reading and learning are two concepts, the real operation is an effective way to test knowledge, practice is full of loopholes, we should always knock the code to find a feeling.

Python3 is recommended for development, Python2 will be suspended for protection in 2020, and Python3 will be the mainstream. IDE chooses pycharm, sublime or jupyter, etc., and the editor recommends the use of pychram, which is similar to eclipse in Java. Browsers learn to use Chrome or FireFox browsers to check elements and use them to grab packages. To understand the reptiles and libraries of the mainstream, such as urllib, requests, re, bs4, xpath, json, etc., it is necessary to master the common reptile structure scrapy.

3. Conduct practical exercises

Have crawler ideas, independently design crawler system, find some websites to do exercises. Grasp the requirements of the crawling strategies and methods of static web pages and dynamic web pages, understand the web pages loaded by JS, understand selenium+PhantomJS imitating browsers, and know how to deal with json pattern data. Web page POST request, to input data parameters, and this kind of web page is generally dynamically loaded, the need to grasp the package method. If you want to improve the power of the crawler, you have to consider the use of multi-threading, multi-process collaboration or distributed operations.

4. learn the foundation of database to deal with large-scale data storage.

When the amount of data crawled back is small, it can be stored in the form of a document, but a large amount of data will not work. Therefore, it is necessary to master a database and learn the more mainstream MongoDB at present. It is convenient to store some unstructured data, and the knowledge of the database is very simple, mainly for data storage and extraction, and then learn when needed.

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