Oops, try again. Your function fails on purify([4, 5, 5, 4]). It returns [4, 5, 4] when it should return [4, 4].
I expected it to complete successfully, but it's not removing all of the odd numbers for a reason I don't understand.
def purify (numbers): for x in numbers: if x%2==1: numbers.remove(x) return numbers