I think it is not too unzen in its aim and method but if you ask there many little tricks that I'd say are unzen. First, give all the code a pass of autopep

I think it is not too unzen in its aim and method but if you ask there many little tricks that I'd say are unzen. First, give all the code a pass of autopep8 comb. Second, avoid things like "lambda (op,num): (num, -num)[...], just use "x if y else z" Then you wouldn't be too far from Norvig's little educational gems.