The most straightforward way seems to use an external iterator to keep track. Note that this answer considers that you're looping on same sized lists.
example
a = [10, 12, 14, 16, 18] b = [10, 8, 6, 4, 2] for i in range(len(a)): print(a[i] + b[i])
Output
This will give the output −
20 20 20 20 20
Example
You can also use the zip method that stops when the shorter of a or b stops.
a = [10, 12, 14, 16, 18] b = [10, 8, 6] for (A, B) in zip(a, b): print(A + B)
Output
This will give the output −
20 20 20