Pairwise (a.k.a. all-pairs) testing is an effective test case generation technique that is based on the observation that most faults are caused by interactions of at most two factors. Pairwise-generated test suites cover all combinations of two therefore are much smaller than exhaustive ones yet still very effective in finding defects.

http://www.pairwise.org/tools.asp

This morning, I spend 30 mins to fork allpair perl code to python, 300 lines in then suddenly I just thought, why don't I just google it there must be sth in python already and there they are allpair in python, awesome.