Python list.index throws exception when index not found

Question

Why does list.index throw an exception, instead of using an arbitrary value (for example, -1)? What\'s the idea behind this?

To me it looks cleaner to d

Answer 1

Well, the special value would actually have to be None, because -1 is a valid index (meaning the last element of a list).

You can emulate this behavior by:

idx = l.index(x) if x in l else None