Python · Lesson 5 of 9

Loops

for loops with range(), looping over lists, while, break and continue.

for repeats once for every item in a sequence. range(start, stop) produces numbers up to (not including) stop.

while repeats as long as a condition is true — make sure something inside changes so it eventually stops.

break leaves the loop immediately; continue skips to the next round. enumerate(items) gives you the position and the item together.

Try it yourself

Code editor

Press Run to see the output.

Edit and press Run (or Ctrl/⌘ + Enter). Python runs in your browser — the first run downloads the Python engine and takes a few seconds.

Which numbers does range(2, 5) produce?

2, 3, 4, 5 2, 3, 4 3, 4, 5 0 to 5

Print the multiplication table of 9 from 9 × 1 to 9 × 10 using a for loop and an f-string.

How would you loop over a dictionary's keys and values?

Use .items(): for key, value in data.items(): ... — it yields pairs.

What does the else clause on a loop do?

A loop's else block runs only if the loop finished without hitting break. It is handy for search loops: else means 'not found'.