pythonLogic errorEasy

Even-number total adds up the odd ones

Time: 0:00

BugFind the bug and fix the code

What it should do

sum_evens(nums) adds up only the even numbers. Example: sum_evens([1, 2, 3, 4]) → 6.

What happens instead

sum_evens([1, 2, 3, 4]) returns 4, which is 1 + 3.

def sum_evens(nums):
    total = 0
    for n in nums:
        if n % 2:
            total += n
    return total

Test a custom input to verify an edge case (e.g. empty lists, negative numbers, duplicates).

⏱️0:00

Hints

🏆 0 hints = Flawless Solve

Hint 2

Unlocks after Hint 1

Hint 3

Unlocks after Hint 2

This bug belongs to the logic errors pattern

The wrong operator, an inverted condition, a formula the right way round but backwards.

Learn the logic errors pattern Step through your own code

Spoiler: why this bug happens(try it first; the hints get warmer one at a time)

What went wrong: n % 2 is 0 for even numbers, and 0 counts as false. So if n % 2 picks the odd numbers.

The fix: if n % 2 == 0:

Remember: write the full comparison instead of relying on 0 meaning false.

The pattern behind it: logic errors.

More logic errors to practise

Embed this challenge on your site

Paste this into any web page or blog post. Visitors fix the bug right there, in their browser.

<iframe src="https://trybughunt.com/embed/2ecd5979-9bc6-46ba-802d-37c2d9ad90a9" title="Debugging challenge: Even-number total adds up the odd ones" width="100%" height="580" loading="lazy" style="border:1px solid #d4d4d8;border-radius:12px;max-width:760px"></iframe>
<p style="font-size:14px">Debugging challenge from <a href="https://trybughunt.com/challenges/2ecd5979-9bc6-46ba-802d-37c2d9ad90a9">TryBugHunt</a></p>

pythonLogic errorEasy

Even-number total adds up the odd ones

Time: 0:00

BugFind the bug and fix the code

What it should do

sum_evens(nums) adds up only the even numbers. Example: sum_evens([1, 2, 3, 4]) → 6.

What happens instead

sum_evens([1, 2, 3, 4]) returns 4, which is 1 + 3.

def sum_evens(nums):
    total = 0
    for n in nums:
        if n % 2:
            total += n
    return total

Test a custom input to verify an edge case (e.g. empty lists, negative numbers, duplicates).

⏱️0:00

Hints

🏆 0 hints = Flawless Solve

Hint 2

Unlocks after Hint 1

Hint 3

Unlocks after Hint 2

This bug belongs to the logic errors pattern

The wrong operator, an inverted condition, a formula the right way round but backwards.

Learn the logic errors pattern Step through your own code

Spoiler: why this bug happens(try it first; the hints get warmer one at a time)

What went wrong: n % 2 is 0 for even numbers, and 0 counts as false. So if n % 2 picks the odd numbers.

The fix: if n % 2 == 0:

Remember: write the full comparison instead of relying on 0 meaning false.

The pattern behind it: logic errors.

More logic errors to practise

Embed this challenge on your site

Paste this into any web page or blog post. Visitors fix the bug right there, in their browser.

<iframe src="https://trybughunt.com/embed/2ecd5979-9bc6-46ba-802d-37c2d9ad90a9" title="Debugging challenge: Even-number total adds up the odd ones" width="100%" height="580" loading="lazy" style="border:1px solid #d4d4d8;border-radius:12px;max-width:760px"></iframe>
<p style="font-size:14px">Debugging challenge from <a href="https://trybughunt.com/challenges/2ecd5979-9bc6-46ba-802d-37c2d9ad90a9">TryBugHunt</a></p>

Even-number total adds up the odd ones

What it should do

What happens instead

More logic errors to practise

Related errors

Even-number total adds up the odd ones

What it should do

What happens instead

More logic errors to practise

Related errors