Chapter 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.

Note

These functions behave as if they are proper, lazy, Python iterables. Some of them create intermediate objects, however; this leads to them consuming a large amount of memory. Since implementations may change with Python releases, we can't provide function-by-function advice here. If you have performance or memory issues, ensure that you check the implementation. "Use...