My son showed me this cool web site that allows him to practice python code in his browser called repl.it. It doesn't just work for Python, but also works for languages like PHP and C#, and many others, including web frameworks like Django. All of this, the code editor and executing the code runs in the browser, so you don't need the code to run on your machine and you don't need to install any kind of editor.
There's other sites like this that I'm aware of, but what caught my interest is that I can use this free site to embed a code listing on my web site and a person can also run my code in a window on my web site. The code is displayed right on my site and it is displayed on my site when it runs too, so my visitors don't have to leave my site to view, edit, or run the code.
Oh, and as I just mentioend, I can display code and a visitor can edit it before they run it.
Let me show you an example that would explain it much better than words will.
It should be obvious that this is great for education purposes. If you wanted to teach people how to code in any of the many languages supported by repl.it, then you can have the code you want to demonstrate right on your web site. And not only can you show the code, you can let your visitors edit and run it.
You can go ahead and edit any of the code in the editor and run it. repl.it will simply create a new version of the file.
This has amazing possibilities for anybody who wants to learn or teach coding.
Repl.it is free with paid upgrades.