Singleton

The singleton pattern restricts the instantiation of a class to one object, which is useful when you need one object to coordinate actions for the system.

The basic idea is that only one instance of a particular class, doing a job, is created for the needs of the program. To ensure that this works, we need mechanisms that prevent the instantiation of the class more than once and also prevent cloning.

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...