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

Here's a one liner using list comprehensions, w/o other libraries:

list3 = [sub[i] for i in range(len(list2)) for sub in [list1, list2]] + [list1[-1]]

Here is another approach, if you allow alteration of your initial list1 by side effect:

[list1.insert((i+1)*2-1, list2[i]) for i in range(len(list2))]