How to get the cartesian product of a series of lists

Use itertools.product, which has been available since Python 2.6.

import itertools

somelists = [
   [1, 2, 3],
   ['a', 'b'],
   [4, 5]
]
for element in itertools.product(*somelists):
    print(element)

This is the same as:

for element in itertools.product([1, 2, 3], ['a', 'b'], [4, 5]):
    print(element)