What foundation is needed for python crawler

Starting with a crawler does not require you to be proficient in Python programming, but basic knowledge cannot be ignored. So what Python basics do we need?

First of all, let’s take a look at the simplest crawler process:

The first step To Determine the link of the crawled page. Since we usually crawl more than one page of content, we should pay attention to the change of the link when the page is turned and the keyword changes. Sometimes we even need to consider the date; in addition, the main web page needs to be static, Dynamically loaded.

The second step Request resources, this is not difficult, mainly the use of Urllib and Request libraries, just read the official documents when necessary

The third step is to parse the web page. After the resource request is successful, the source code of the entire web page is returned. At this time, we need to locate and clean the data

When it comes to data, the first point to pay attention to is the type of data. Should you master it?

Secondly, the data on the web page is often arranged very neatly, thanks to the list. Most web page data is neat and regular, so do you need to master lists and loop statements too!

But it is worth noting that the web page data is not necessarily neat and regular. For example, the most common personal information, except for the required options, I don’t like to fill in other parts. At this time, some information is missing. You have to first determine whether there is data before crawling, so the judgment statement cannot be less!

After mastering the above content, our crawler can basically run, but in order to improve the code efficiency, we can use functions to divide a program into multiple small parts, each part is responsible for a part of the content, so that we can You need to mobilize a function multiple times. If you are more powerful and develop a crawler software in the future, do you need to master another class?

The fourth step is to save the data, is it necessary? First open the file, write data, and finally close it, so do you still need to master the reading and writing of files?

So, The most basic Python knowledge points you need to master are:

#So, if you want to learn crawling, you can get twice the result with half the effort only by mastering the above Python-related knowledge.

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