In this chapter, we looked at a number of functions in the itertools module. This library module provides a number of functions that help us work with iterators in sophisticated ways.

We looked at the product() function that will compute all the possible combinations of the elements chosen from two or more collections. The permutations() function gives us different ways to reorder a given set of values. The combinations() function returns all the possible subsets of the original set.

We also looked at ways in which the product() and permutations() functions can be used naively to create extremely large result sets. This is an important cautionary note. A succinct and expressive algorithm can also involve a vast amount of computation. We must perform basic complexity analysis to be sure that the code will finish in a reasonable amount of time.

In the next chapter, we'll look at the functools module. This module includes some tools to work with functions as first-class objects. This builds on some material shown in Chapter 2, Introducing Essential Functional Concepts, and Chapter 5, Higher-Order Functions.