Select the other of 2 items in a list

[bowlofred]

In your attempt above, if these are really lists then the opponent = pieces isn't useful because it's just referencing the pieces list, so any modification will modify both. I'm assuming that pieces already exists and that you don't want to change it.

If so, I'd use a comprehension to pull out everything that doesn't match. This doesn't check that there are really only two elements, or that piece is present as one of the elements. But if both are true, it will return the other element.

opponent = [x for x in pieces if x != piece][0]