The singleton pattern
The singleton pattern is one of the most controversial patterns; many have accused it of being an "anti-pattern", a pattern that should be avoided, not promoted. In Python, if someone is using the singleton pattern, they're almost certainly doing something wrong, probably because they're coming from a more restrictive programming language.
So why discuss it at all? Singleton is one of the most famous of all design patterns. It is useful in overly object-oriented languages, and is a vital part of traditional object-oriented programming. More relevantly, the idea behind singleton is useful, even if we implement that idea in a totally different way in Python.
The basic idea behind the singleton pattern is to allow exactly one ...
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