Clever solution!

Late reply, but you subtract one number from the "num_pill" since there exist only one space/distance in between two pillars. Same as all real life objects, there exist only one space in between two objects.

number of pillars (≥ 1) is given to us. We have no need to check it in our code

what is num_pill - 1 ?
sorry I can't understand.

This would need input validation in produciton as entering a negative integer produces incorrect results. For example, entering -1 pillars returns -4000

resolve katas sometime like translation.your answer deserve “信，雅，达。”

numeric value of true is 1

numeric value of false is 0

i always forget True being 1 and False being 0. nice code

Won't this unnecessarily perform calculations which could be bypassed by testing for 1 pillar?

I've passed all the tests apart from the first edge case test. Any ideas?

Ooooh, I didn't realise it meant a list. Sorry about obvious spoilers. Thanks a lot for the help.

Woops, you're damn right about the location of the error, sorry... :/ (I need holidays, it seems...).

Tho, it still stands that the problem is in your code: the check function fails because you send to it an int instead of a sequence, meaning a list. ;)

Note: when you post code, don't forget the spoiler flag and use proper markdowns so that it's easier to read it.

EDIT: I see that there are no visible expected outputs in the sample tests. That's unfortunate... you need to return lists of integers, here.