Pythonic way to combine two lists in an alternating fashion?

Question

I have two lists, the first of which is guaranteed to contain exactly one more item than the second. I would like to know the most Pythonic way to create a

Answer 1

This is nasty but works no matter the size of the lists:

list3 = [element for element in list(itertools.chain.from_iterable([val for val in itertools.izip_longest(list1, list2)])) if element != None]