import itertools print map("".join, itertools.product(*["123", "257", "998"]))
Standard input is empty
['129', '129', '128', '159', '159', '158', '179', '179', '178', '229', '229', '228', '259', '259', '258', '279', '279', '278', '329', '329', '328', '359', '359', '358', '379', '379', '378']