As noted in the previous chapters, Python's for loop works with collections. When working with materialized collections such as tuples, lists, maps, and sets, the for loop involves the explicit management of states. While this strays from purely functional programming, it reflects a necessary optimization for Python. If we assume that state management is localized to an iterator object that's created as a part of the for statement evaluation, we can leverage this feature without straying too far from pure, functional programming. If, for example, we use the for loop variable outside the indented body of the loop, we've strayed from purely functional programming by leveraging this state control variable.
We'll return ...
