You are learning to program, then "reptiles" is definitely something you can't ignore. So what preparations are needed before learning Python crawlers?

A love of learning, indomitable heart

A computer with a keyboard (what system is OK. I use os x, so the example will be based on this)

Html related knowledge. Do not need proficiency, can understand a bit on the line

Python's basic grammar knowledge.

Four tools for beginners to write Python crawlers

When these are all you have, you need to learn this time:

0. Basic crawler works

1. Basic http crawler: scrapy

2.Bloom Filter: Bloom Filters by Example

3. If you need large-scale web crawling, you need to learn the concept of distributed crawlers. In simple terms, you just need to learn how to maintain a distributed queue that all cluster machines can effectively share. The simplest implementation is python-rq: https://github.com/nvie/rq

The combination of 4.rq and Scrapy:darkrho/scrapy-redis · GitHub

5. Follow-up processing: webpage extract (grangier/python-goose · GitHub), storage (Mongodb)

Four tools for beginners to write Python crawlers

Python's fire is largely due to a variety of easy-to-use modules that are commonly found on home travel crawl sites.

NO.1 F12 Developer Tools

Look at the source code: quickly locate the elements

Analysis xpath: 1, here Google recommends browser, you can right-click in the source interface

Four tools for beginners to write Python crawlers

NO.2 capture tool

Recommended httpfox, the plug-in under Firefox browser, is better than Google Firefox's own F12 tool, you can easily check the information received by the website

Four tools for beginners to write Python crawlers

NO.3 XPATH CHECKER (Firefox plugin)

Four tools for beginners to write Python crawlers

Very good xpath testing tool, but there are also a few minor drawbacks:

The xpath checker generates absolute paths, encounters some dynamically generated icons (commonly there are list page buttons, etc.), and erratic absolute paths are likely to cause errors, so here's a suggestion for real analysis, just for reference.

Remember to remove the "x:" from the xpath box below. This looks like this is the syntax of an earlier version of xpath. It is currently incompatible with some modules (such as scrapy) or deleted to avoid errors.

Four tools for beginners to write Python crawlers

NO.4 Regular Expression Test Tool

Online regular expression testing, used to practice more hands, but also assist analysis! There are many ready-made regular expressions that can be used and referenced!

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