"If you spend long enough in the programming world, you'll come across the term singleton at some point. And if you hadn't seen this term yet, well, now you have! In Python, you don't need singleton classes. Almost never. But creating one is a great exercise in understanding how Python creates objects. And discussing alternatives to a singleton class helps you explore other aspects of Python."
"The singleton pattern is a design pattern in which a class can produce only one instance. Not two, not three, just one. And each time you try to create a new instance of a singleton class, you get the same object again. Let me pick a trivial example of when you may need this. You're writing a game. Perhaps several players can play games simultaneously. And you need a leaderboard. But you only want one leaderboard."
".add_score() adds a score to the leaderboard, as its name implies. If the player already exists in the .scores dictionary, you add to their points tally. If the player doesn't exist yet, you add them to the dictionary. There are neater ways to write this method, but this will do here. .get_leaderboard() returns a sorted list containing the players in order, from those with the highest number of points to the lowest."
Singleton pattern enforces that a class can produce only one instance and returns the same object on every instantiation. Python rarely needs formal singleton classes, but implementing one clarifies Python's object creation mechanisms and alternatives. Common singleton use cases include a shared leaderboard in a multiplayer game, single database or hardware connections, loggers, and configuration managers. Example methods for a leaderboard include .add_score() to update a .scores dictionary and .get_leaderboard() to return players sorted by descending points. Implementations can be simplified or replaced by module-level singletons, dependency injection, or shared objects passed explicitly.
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