Python Control Flow: if, Loops & match

3Control Flow: if, Loops & match

The rules, again

Same game as chapter 1: read the question, commit to a prediction, run it, and only then open the answer. Wrong prediction means the drill goes on your redo list for three days from now.

Control flow looks like the most boring chapter in any language. Python hides real surprises in it: an else that belongs to a loop, a match statement that assigns when you thought it compared, and the ancient continue-skips-the-update infinite loop that still catches seniors on whiteboards.

Learn the concepts first

Rusty on the basics? Work through Conditions and Loops on learnpython.org first, then come back and drill.

One idea before you start

Most loop drills in this chapter come down to knowing exactly what a for loop consumes.

Definition

An iterable is anything a for loop can walk through: lists, strings, dicts, ranges, files, generators. The loop asks it for the next value until it runs out. The loop itself never counts indexes, which is why Python has no classic three-part for loop and why tools like enumerate and zip exist.

The drills

Click a question to open it. The answer stays hidden until you ask for it. Predict first.

14 drills. Predict first, then open the answer

Want more drills?

When these stop surprising you, let an AI generate fresh ones. Copy this prompt into ChatGPT, Claude, or any assistant you like:

You are my Python drill coach. Quiz me on: if/elif/else, ternary
expressions, for and while loops, break/continue, for...else,
range() semantics, enumerate, zip, dict iteration, and the match
statement.
 
Rules:
- Ask ONE question at a time. Show a short code snippet and ask me to
  predict the output (or the error) before running it.
- Wait for my answer. Do not reveal anything until I reply.
- If I am right, say so in one line and raise the difficulty slightly.
- If I am wrong, explain the why in 2-3 sentences, then give me a
  similar question later to check I really got it.
- Prefer tricky edge cases over textbook questions: for...else with
  and without break, range(5, 0), zip with unequal lengths, removing
  items from a list while looping, bare-name capture in match cases,
  continue skipping the update in a while loop.
- Keep score. After 10 questions, list the concepts I missed so I can
  add them to my redo list.
 
Start with a medium question.

The predict-first rule matters more than the tool. Whatever generates the questions, always commit to an answer before you look.

Done?

Score yourself honestly and queue up your misses. The two that catch almost everyone: for...else (drill 4) and the match capture trap (drill 13). If you got those on the first try, you know Python's control flow better than most people interviewing you.

Next chapter: data structures, where list, tuple, dict, and set each hide a gotcha and copying a list does less than you think.