The previous three examples combined additional processing with mapping. Combining processing with filtering doesn't seem to be quite as expressive as combining with mapping. We'll look at an example in detail to show that, although it is useful, it doesn't seem to have as compelling a use case as combining mapping and processing.
In Chapter 4, Working with Collections, we looked at structuring algorithms. We can easily combine a filter with the structuring algorithm into a single, complex function. The following is a version of our preferred function to group the output from an iterable:
from typing import Iterator, Tupledef group_by_iter(n: int, items: Iterator) -> Iterator[Tuple]: row = tuple(next(items) ...
