Building sets – literals, adding, comprehensions, and operators

If we've decided to create a collection based on only an item being present—a set —we have several ways of building this structure. Because of the narrow focus of sets, there's no ordering to the items – no relative positions – and no concept of duplication. We'll look at a number of ways we can assemble a set collection from individual items.

In some cases, we'll need a set because it prevents duplicate values. It's common to summarize data by reducing a large collection to a set of distinct items. An interesting use of sets is for locating repeated items when examining a connected graph. We often think of the directories in the filesystem forming a tree from the root directory through a path of directories to a particular file. Because there are links in the filesystem, the path is not a simple directed tree, but can have cycles. It can be necessary...