Recall

This chapter looked at a design pattern that seems ubiquitous in Python, the iterator. The Python iterator concept is a foundation of the language and is used widely. In this chapter we examined a number of aspects:

• Design patterns are good ideas we see repeated in software implementations, designs, and architectures. A good design pattern has a name, and a context where it's usable. Because it's only a pattern, not reusable code, the implementation details will vary each time the pattern is followed.
• The Iterator protocol is one of the most powerful design patterns because it provides a consistent way to work with data collections. We can view strings, tuples, lists, sets, and even files as iterable collections. A mapping contains a number of iterable collections including the keys, the values, and the items (key and value pairs.)
• List, set, and dictionary comprehensions are short, pithy summaries of how to create a new collection from an...