It's no bad thing to import modules if they get the job done! There's a time and a place for code golf. That said - with the distance of several years' hindsight - I should probably have added a short comment.

Really nice! I saw someone else use a for-loop with an xor operator (i.e. "^") which is similar and doesn't need an import. I like this the best because it is O(n) and it is very clean. It's a bit more arcane than the simplest solution, but for large values of N this is definitely the right approach.

Good work :)

Your post was visible in the homepage, that's why you should use spoiler flag here.

Why is this a spoiler? I'm not providing a different solution, I'm explaining why this solution is faster than others.

PS I get it. It compares 2 solutions and one of them is not here. Sorry about that.

Please use spoiler flag next time.

There's no need for the condition because it returns 0 by default

I thought it returns False if the array is empty

it defaults to 0 when you would think it's 'null'

However, s is better that str because str is a built-in type in python

yep, but the inputs are too small in the test suite (at least when I posted this), so that worked with py3 too, while it's incorrect.