the initial code returns an empty list though, this is misleading

hmm return tuple ? ;) (round brackets)

Fractions will be presented as an array/tuple (depending on the language)

and the reduced fraction must be returned as an array/tuple:

In Python your code should return a tuple, not a list. Not a kata issue.

The test cases need to be changed for python to have square brackets instead of round ones. I have the right answer, but, since I'm returning a list(array), my return value has square brackets while it is expecting round brackets. That's the only thing wrong with my answer and it's quite frustrating.