Beginner → Intermediate
Python Mastery — The Complete Interactive Course
From your first print() to functions, scope and recursion. Every example runs against a real Python interpreter in your browser, every exercise is graded by executing your code against hidden tests, and the Visualizer steps through a program one line at a time so you can watch the variables change.
The course
Not loading? Open the course in its own tab.
Common questions
Do I need to install Python to take this course?
No. The course runs a teaching Python 3 interpreter inside your browser. Nothing is installed, nothing is sent anywhere, and there is nothing you can break.
How much of Python does it cover?
It covers 16 modules — from your first program through types, operators, control flow, loops, strings, lists, tuples, sets, dictionaries, copying semantics, functions, scope and recursion. Modules on files, exceptions, classes, generators, decorators and concurrency are written but not yet verified, so the course lists them in its curriculum tab rather than publishing them as if they were ready.
Is the Python course free?
Yes. Every lesson, the graded exercises and the timed drill are free and need no account.
Are the exercises actually graded?
Yes. Your function is executed against 167 assertions — some shown, some hidden and aimed at edge cases. The tests check behaviour, never the text of your code, so any correct solution passes.
Can I see how the code runs, step by step?
Yes. The console has a Visualizer that steps through your program one line at a time and shows every variable as it changes, alongside plain-English explanations of the error types beginners hit first.