Starting

Scraping is just downloading a webpage and getting the wanted information from it. As a start you can scrape the README.md

I’ll use khttp for the kotlin implementation because of the ease of use, if you want something company-tier I’d recommend OkHttp.

Update: I have made an okhttp wrapper for android apps, check out NiceHttp

1. Scraping the Readme

Python

import requests
url = "https://recloudstream.github.io/devs/scraping/"
response = requests.get(url)
print(response.text)  # Prints the readme

Kotlin

In build.gradle:

repositories {
    mavenCentral()
    jcenter()
    maven { url 'https://jitpack.io' }
}

dependencies {
	// Other dependencies above
	compile group: 'khttp', name: 'khttp', version: '1.0.0'
}

In main.kt

fun main() {
    val url = "https://recloudstream.github.io/devs/scraping/"
    val response = khttp.get(url)
    println(response.text)
}

2. Getting the github project description

Scraping is all about getting what you want in a good format you can use to automate stuff.

Start by opening up the developer tools, using

Ctrl + Shift + I

or

f12

or

Right click and press Inspect

In here you can look at all the network requests the browser is making and much more, but the important part currently is the HTML displayed. You need to find the HTML responsible for showing the project description, but how?

Either click the small mouse in the top left of the developer tools or press

Ctrl + Shift + C

This makes your mouse highlight any element you hover over. Press the description to highlight up the element responsible for showing it.

Your HTML will now be focused on something like:

<p class="f4 mt-3">
      Work in progress tutorial for scraping streaming sites
</p>

Now there’s multiple ways to get the text, but the 2 methods I always use is Regex and CSS selectors. Regex is basically a ctrl+f on steroids, you can search for anything. CSS selectors is a way to parse the HTML like a browser and select an element in it.

CSS Selectors

The element is a paragraph tag, eg <p>, which can be found using the CSS selector: “p”.

classes helps to narrow down the CSS selector search, in this case: class="f4 mt-3"

This can be represented with

p.f4.mt-3

a dot for every class full list of CSS selectors found here

You can test if this CSS selector works by opening the console tab and typing:

document.querySelectorAll("p.f4.mt-3");

This prints:

NodeList [p.f4.mt-3]

NOTE: You may not get the same results when scraping from command line, classes and elements are sometimes created by javascript on the site.

Python

import requests
from bs4 import BeautifulSoup  # Full documentation at https://www.crummy.com/software/BeautifulSoup/bs4/doc/

url = "https://github.com/Blatzar/scraping-tutorial"
response = requests.get(url)
soup = BeautifulSoup(response.text, 'lxml')
element = soup.select("p.f4.mt-3")  # Using the CSS selector
print(element[0].text.strip())  # Selects the first element, gets the text and strips it (removes starting and ending spaces)

Kotlin

In build.gradle:

repositories {
    mavenCentral()
    jcenter()
    maven { url 'https://jitpack.io' }
}

dependencies {
	// Other dependencies above
	implementation "org.jsoup:jsoup:1.11.3"
	compile group: 'khttp', name: 'khttp', version: '1.0.0'
}

In main.kt

fun main() {
    val url = "https://github.com/Blatzar/scraping-tutorial"
    val response = khttp.get(url)
    val soup = Jsoup.parse(response.text)
    val element = soup.select("p.f4.mt-3") // Using the CSS selector
    println(element.text().trim()) // Gets the text and strips it (removes starting and ending spaces)
}

Regex:

When working with Regex I highly recommend using (regex101.com)[https://regex101.com/] (using the python flavor)

Press Ctrl + U

to get the whole site document as text and copy everything

Paste it in the test string in regex101 and try to write an expression to only capture the text you want.

In this case the elements is

<p class="f4 mt-3">
      Work in progress tutorial for scraping streaming sites
    </p>

Maybe we can search for <p class="f4 mt-3"> (backslashes for “)

<p class=\"f4 mt-3\">

Gives a match, so lets expand the match to all characters between the two brackets ( p>…</ ) Some important tokens for that would be:

  • .*? to indicate everything except a newline any number of times, but take as little as possible
  • \s* to indicate whitespaces except a newline any number of times
  • (*expression inside*) to indicate groups

Which gives:

<p class=\"f4 mt-3\">\s*(.*)?\s*<

Explained:

Any text exactly matching <p class="f4 mt-3"> then any number of whitespaces then any number of any characters (which will be stored in group 1) then any number of whitespaces then the text <

In code:

Python

import requests
import re  # regex

url = "https://github.com/Blatzar/scraping-tutorial"
response = requests.get(url)
description_regex = r"<p class=\"f4 mt-3\">\s*(.*)?\s*<"  # r"" stands for raw, which makes blackslashes work better, used for regexes
description = re.search(description_regex, response.text).groups()[0]
print(description)

Kotlin In main.kt

fun main() {
    val url = "https://github.com/Blatzar/scraping-tutorial"
    val response = khttp.get(url)
    val descriptionRegex = Regex("""<p class="f4 mt-3">\s*(.*)?\s*<""")
    val description = descriptionRegex.find(response.text)?.groups?.get(1)?.value
    println(description)
}

Next up: Properly scraping JSON apis

Edit on GitHub

If you see a mistake here, you can open a pull request