itertools - izip

• izip

Python 3 does not need this any more as the built-in zip is already an iterator.

Combine two unbounded lists

from itertools import izip, count

for t in izip(count(start=1, step=1), count(start=10, step=-1)):
    print("{:3} + {:3} = {}".format(t[0], t[1], t[0]+t[1]))
    if t[0] > 20:
        break
#  1 +  10 = 11
#  2 +   9 = 11
#  3 +   8 = 11
#  4 +   7 = 11
#  ...
# 20 +  -9 = 11
# 21 + -10 = 11