IndexError: loop runs past a short list

What this problem practises

Loops are where off-by-one bugs live. range() excludes its stop value, the loop variable keeps its last value even after the loop ends, and break versus continue changes the flow in ways that are easy to misread when you skim.

This is a fix-the-bug problem: a short program is given in its broken state, and the task is to repair the code so it produces the required output. The interactive editor runs your fixed version in the browser and checks it for you — no setup, no local interpreter.

Difficulty: easy — the fix or the trick is normally a single line, and a careful read should be enough.

The challenge

This program should print 5 and 13, but the loop reaches index 3 which does not exist. Fix the range so it prints both numbers, one per line.

The code runs in PyDebug’s in-browser compiler. Open the problem, run the snippet, watch the exact error or output, and keep iterating until it is right. Signed-in solves count toward XP and your daily streak.

The snippet

The interactive editor pre-fills exactly this code, broken and ready to repair:

nums = [5, 13]
for i in range(4):
    print(nums[i])

More loops problems

• IndexError: loop runs past a short list easy
• IndexError: loop runs past a short list easy
• TypeError: looping directly over a number easy

Keep going

• Python debugging guide — a systematic method for finding bugs like this one fast.
• Browse every loops problem in this topic.
• Common Python errors and what they actually mean, plus the Python glossary for any term used on this page.