haha 100 %

This isn't quite correct. That isn't a list expression, its a lazy generator. There is no intermediate list of 1s created, rather it yeilds a 1 each time it is requested by the sum function.

they were?

real.

Not a kata suggestion

its really a 8 kyu problem because it requires a basic knowledge about characters

Then why do you keep doing them? Skip them if you don't like them, nobody forces you to do them. Seriously, what's the "obscure formula" you had to google here?

I disagree with you, that's not the only way to solve this kata. And some solutions don't need "obscure" formulas at all.

It is a puzzle, I think description is fine as it is.

list comprehension

Added regex tag for the Kata