Element-wise addition of two list of different lengths?

Question

How to perform element-wise addition of different length lists?
Assuming \"0\" for missing elements.
Note: len(a) will always be less than or equal to len(b)

exa

Answer 1

you can pad a with zeroes like this and use sum

a=[1,2,3]
b=[1,2,3,4,5]
a[:] = [a[i] if i < len(a) else 0 for i,j in enumerate(b)]
result=[sum(n) for n in zip(a,b)]
print result

results in

[2, 4, 6, 4, 5]