Using combinatorial functions in the itertools module
Python 2.2 introduced simple generators to the Python language and reconceived standard loops in terms of underlying iterators. With Python 2.3, generators become standard (no need for _future_), and the new module itertools is introduced to work flexibly with iterators. The itertools module is essentially a set of combinatorial higher-order functions, but ones that work with lazy iterators rather than with finite lists. In this installment, David explores the new module, and gives you a sense of the new expressive power available with combinatorial iterators."