8
The Itertools Module

Functional programming emphasizes stateless objects. In Python, this leads us to work with generator expressions, generator functions, and iterables, instead of large, mutable collection objects. In this chapter, we’ll look at elements of the itertools library. This library has numerous functions to help us work with iterable sequences of objects, as well as collection objects.

We introduced iterator functions in Chapter 3, Functions, Iterators, and Generators. In this chapter, we’ll expand on that superficial introduction. We used some related functions in Chapter 5, Higher-Order Functions.

There are a large number of iterator functions in the itertools module. We’ll examine the combinatoric functions in the next chapter. In this chapter, we’ll look at the following three broad groupings of the remaining iterator functions:

• Functions that work with potentially infinite iterators. These can be applied to any iterable...