About PyLearn

PyLearn teaches Python the way most people actually learn it: by writing small programs and finding out immediately whether they work. Each lesson pairs a short explanation with an editor, a console and a set of tests.

How the code runs

There is no execution server. PyLearn ships CPython compiled to WebAssembly and runs it inside a Web Worker in your own browser, so your code never travels over the network, the platform costs nothing to run, and an accidental infinite loop stops at five seconds instead of taking the page with it.

The data courses need NumPy and pandas, which are several megabytes each. They are fetched only by the lessons that ask for them and then kept for the rest of your visit, so you wait once rather than once a lesson. The courses that talk to an API use a scripted stand-in for the network, because a browser has no sockets — which also happens to be how you would test an API client for real.

How grading works

Every exercise carries hidden tests. When you press Check, your code is executed in a fresh namespace and each test is run against it — calling your functions, reading your variables, or comparing what you printed. A failing test tells you what it expected and what it got, and hints unlock as you keep trying.

What it costs

Four courses, forty lessons, every quiz, every project and every cheatsheet are free, along with your XP, badges, streaks and certificates. Pro is $5 a month or $48 a year and adds two advanced courses — data analysis with NumPy and pandas, and APIs with async Python — plus twenty-four further lessons, the capstone project, unlimited quiz retakes and downloadable PDFs.

The first lessons of a Pro course are readable in full rather than cut off mid-sentence, and if a subscription lapses nothing you earned is taken away: the Pro lessons re-lock, and your progress, XP, badges and certificates stay exactly where they were.

What it does not do

No forums, no feeds, no notification emails you did not ask for, and no AI tutor reading your work. It is a course and a code editor.