Say good-bye to the manual! Use this library to make it easy for the pages to roll

Handle dynamic web grab: full guide for requests-HTML scrolling and unlimited scrolling

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Have you ever experienced the dilemma of getting only part of the content when accessing a web page with an ordinary reptile, where data that need to be rolled to load are never available? Don't worry, this paper will take you to solve this problem once and for all and to meet the capture challenge of rolling loads and unlimited scroll pages easily through the requests-HTML library. After reading this paper, you will have the core skills of dynamic content capture and be able to handle complex web-page loadings。

Knowledge of requests-HTML: the sharper to capture dynamic web pages

Requests-HTML is a pytho designed for humansNic HTML resolution library, which not only inherits the ease of use of requests, but also adds powerful javasCript rendering capability perfected the capture problem of dynamic loading。

The core code of the project is centralized in the document requests HTML. Py, where the official document details its functionality and method of use, and you can get more details through the docs/source/index. Rst。

Scroll loading principle: why ordinary reptiles cannot do it

In traditional web pages, all content is usually transferred to the client at the time of initial loading. However, modern web pages are increasingly using dynamic loading techniques, which only go through javas when users scroll to a specific locationCript loads more. This technology not only enhances user experience but also challenges data capture。

Requests-HTML solves this problem by integrating pypeteer (a headless chrome browser). It can simulate real user browsing behavior, including scrolling pages, thereby triggering javasCript execution, load dynamic content. This core function is achieved in the render() and arender() approaches of requests HTML. Py。

Basic preparedness: environmental set-up and initialization

Before we start, we need to install the requests-HTML library. Pipenv is recommended for installation to ensure reliance on environmental consistency:

I can't believe it

When the installation is complete, we can create an HTML mission, which is the basis for our interaction with the web page:

From requests HTML iMport HTMLsession
session = HTMLsession()

If you prefer a walk-by program, you also have access to asyn tmlssession:

From requests HTML iI'm sorry, i'm sorry. Asyn(tmlssession)

Roll load realization: core parameter resolution

Requests-HTML provides a render() approach to javasCript render and scroll load. Its core parameters include:

Let's see a basic rolling example:

= session. Get()'https://example. Com/info-scrollI'm sorry. R. HTML. Render

This code simulates the user scroll page 10 times and waits for one second each to ensure that content is loaded with sufficient time。

Unlimited rolling grabs: actual cases

Infinite scrolling is a special form of scroll loading, where pages load new content as users scroll until all content is loaded. To capture such pages, we need to judge when to stop rolling。

Here is a full example of an infinity scroll grab:

From requests HTML iMport HTMLsession
session = HTMLsession()
= session. Get()'https://example. Com/info-scrollI'm sorry.
# number of initial scrolls
scrolldown = 5
# the length of content before storage to determine if there is a new content loaded
=0
while true:
# render page, scroll specified number
i don't know, r. HTML. Render.

# get the current content length
current length =len (r. HTML. HTML)

# if it doesn't add, it's loaded
== sync, corrected by elderman ==
break

# increase the length before updating the number of scrolls
= certificate
scrolldown + = 5
# now r. HTML contains all loads
(f) "successful loading of {scrolldown}scrolling content")

This example, by comparing the length of HTML content before and after rolling, determines whether there are new content loads and is a common strategy for dealing with unlimited rolling。

Advanced skills: custom scroll script

For a more complex rolling scene, we can use sCript parameters execute custom javasCript scroll script. For example, we can scroll to the bottom of the page, or we can scroll to a specific element position:

# script to the bottom of the page
sCript = ""
( ) =
i'm gonna get you out of hereI'm sorry, i'm sorry. Now, return dI don't know.
♪ i'm sorry ♪
"'"
# execute scripts and fetch page height
height = r. HTML. Render(s)Cript=sI'm sorry

This technique is very useful when dealing with scenes that require precise positioning of the rolling position。

Spacing: improving capture efficiency

For scenes that require multiple pages to be captured, step-by-step processing can significantly increase efficiency. A dynamic component of the asyn tmlssession in requests-HTML that can achieve a different pace can be loaded:

Async def fitch and render (url):
= await organization. Get (url)
await r. HTML. Arender (scrolldown=3, sleep=1)
turn around, turn around.
# capture multiple pages simultaneously
reports = await session. Run
imbda: fitch and render'https://example. Com/page1I don't know. Imbda: fitch and render'https://example. Com/page2I don't know. Imbda: fitch and render'https://example. Com/page3I'm sorry. I'm not sure

This approach allows the dynamic loading of multiple pages at the same time, significantly reducing the overall capture time。

Test and debugging: ensure code reliability

To ensure the correctness of the rolling load function, the requests-HTML project provides a comprehensive test example. You can find test codes for various scenarios in tests/test requests HTML. Py files。

Of which, test render() and test async render() method was specially tested for javasCript rendering and scrolling:

I don't know. R = get()
sCript = ""
( ) =
return
width:dI don't knowI'm sorry. Height:dI don't knowI don't know. I'm sorry, i'm sorry.
♪ i'm sorry ♪
♪ i'm sorry ♪
"'"
val = r. HTML. Render(s)Cript=sI don't know. For value in'width'..,'height'..,'device scalefactor':
assert value in val

These test codes not only validate the correctness of the function, but also provide us with examples of what is actually being used。

Common problems and solutions

You may encounter some common problems when you use requests-HTML to process scroll loads. The following are some of the solutions:

Load incomplete: attempt to add the value of sleep parameters to javasCript sufficient time for implementation. Excess memory occupancy: for very long pages, batch capture and processing of data can be considered. Tested as reptiles on the website: use the headers parameter to set up a reasonable user-agent, simulate a real browser. The number of scrolls is difficult to determine: in combination with content change detection and maximum number of scrolls, endless cycles are avoided. Summary and outlook

Through this introduction, you have acquired the core skills of using requests-HTML to process rolling loads and unlimited scroll pages. From the use of basic render() methods to advanced self-defined rolling scripts, to step-by-step efficiency improvements, this knowledge will help you cope with dynamic content capture scenarios。

The source code for requests-HTML projects is valuable for in-depth learning. More detailed api descriptions and examples of use are provided in official documents docs/source/index. Rst。

As web technology continues to evolve, the way dynamic content is loaded will continue to evolve. But with the core principles and methods presented here, you can be flexible in responding to new challenges and easily capture any dynamic web content。

Now is the time to apply this knowledge to practical projects. Have a nice trip on the dynamic page

[free download links]Nic HTML parsing for humanstm

Project address: