Mastering Python Design Patterns - Second Edition

Real-world examples

In a real-life scenario, we can think of the captain of a ship or a boat. On the ship, he is the one in charge. He is responsible for important decisions, and a number of requests are directed to him because of this responsibility.

In software, the Plone CMS has, at its core, an implementation of the singleton. There are actually several singleton objects available at the root of a Plone site, called tools, each in charge of providing a specific set of features for the site. For example, the Catalog tool deals with content indexation and search features (built-in search engines for small sites where you don't need to integrate products like ElasticSearch), the Membership tool deals with things related to user profiles, ...