How to use these pages
Answer the question first, on paper. Then click the answer to unfold it.
Reading a worked answer feels like learning and mostly is not — recognising an answer is a completely different skill from producing one, and only one of them is any use in an exam.
Try it: click this line
That is what every answer on these pages looks like. Nothing is hidden from you — it is hidden from your eye, so that a page of questions stays a page of questions until you have had a go.
In this course there is a second reason to answer first: nearly every answer below is code you can run. Predict, then type it in, then let Python settle the argument. Being wrong at a keyboard costs nothing and teaches more than being right on paper.
Each set follows a concept page — meet the idea there, then come here to make it dependable.
An answer that runs is not automatically right, so several questions ask you to say why something works, or what it would do with input nobody expected. That second habit is the one that survives into The Community App.
Stuck partway through a set? That is the useful part, not a sign you have fallen behind — Getting Unstuck has the method, and Mistakes Are Data has the argument.