does this modify the original list l?

Is it any good to name your arguments/variables str or int, which are normally predefined functions?

I'd rather maintain something like this than a regex. I mean, python is supposed to be about readibility, no? Thanks for this clean solution anyway.

Yup, these should be grouped together.

Because args passed to the spread is a list.

yonax, you uncovered a nasty bug. I have fixed it and added the test cases discussed above to the kata.

This was due to an issue in my logic for solving the problem. It has been corrected, and the kata has been republished.

To confirm,

vector_affinity([None], []) == 0.0 => True

Okay. Then why these tests are not in the kata test cases? :)

vector_affinity([None], [None]) == 1.0
vector_affinity([None], []) == 0.0

Just want to show that mine(incorrect) solution successful pass your test suite and offer one possible way to catch it.

easy enough, but then shouldn't i also add:

test.assert_equals(vector_affinity([None], [None, None, None, None]), .25)
test.assert_equals(vector_affinity([None], [None, None, None, None, None]), .5)
test.assert_equals(vector_affinity([None], [None, None, None, None, None, None, None, None, None, None]), .10)

?

To me knowing that:

vector_affinity([None], [None]) == 1.0
# and
vector_affinity([None], []) == 0.0

should be enough to deduce that None is also a value that counts, and that [None]/[None, None] gets a .5 affinity.
again, it's easy enough to add the test case, but unless that test case addresses a specific flaw in the instructions or problem, i'm hesitant to do so.

Simple, elegant - the entire reason I use codewars is to be enlightened by such answers!

Same solution as the one at the top

Wouldn't max([s2, s1], key=score) be cleaner for the last line?