Codecademy — Learn Python 3

Codecademy’s Python 3 course runs entirely in the browser — no local install, with an in-page editor that checks your code and gives feedback as you go. It moves through syntax, data structures, functions, and object-oriented basics in short, interactive lessons rather than long-form video or text.

The free tier covers a solid beginner path; more advanced modules and projects sit behind a paid subscription. For a similar interactive, no-setup format without the paywall, see LearnPython.org.