while loop with a condition update

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 an output-prediction problem: read the snippet carefully and write down exactly what it prints before anything runs. These questions are interview staples because they test whether you know the language rules, or merely recognise their syntax.

Difficulty: medium — expect to hold two interacting rules in your head at once, such as a boundary combined with a mutation.

The challenge

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 — read it, then submit your prediction:

total = 0
n = 1
while n <= 4:
    total += n * 2
    n += 1
print(total)

More loops problems

• Missing Colon in for Loop easy
• for loop with range and step medium
• enumerate with a start value easy

Keep going

• Output-prediction strategies — how to predict tricky snippets without running them.
• 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.