OP solved it, closing

It shows me an arror when I try this solution

woah I forgot you could do this!

this is definitely my favorite solution to this... wish I'd thought of it.

Wonderful

What I did lol

ugh that looks so satisfying, i love to try and make all my code as compact as possible. how did i not think of this?!?

In Python, you can make another identifier refer to the same function by assignment.

I'm confused. How does this work?

one line alert

Try to solve this on papper and you will see the pattern of numbers.

It is not the 7-th level kata. It requires knowledges of trees, which makes it the 5-th or 6-th level kata.

same +1

Your solution works in both 3.6 and 3.8. There should be no reason for it to fail in one and not the other. It is more likely that you have a small error with an edgecase in your solution, and you managed to not receive a random test with that edgecase when you switched to 3.8.

I have found the answear. The test mode does not work correct for Python 3.8. If you have the same error as mine, just try to test your solution on Python 3.6. It works for me.