Design patterns have a reputation for being over-applied. Someone reads the Gang of Four book, discovers Singleton and Factory, and starts reaching for them everywhere — including places where a plain function would be cleaner and easier to test.
This isn't that kind of post.
The 10 patterns below are the ones that genuinely appear in Django, Flask, FastAPI, and standard library Python. For each one: what it does, where you already encounter it, working code, and an honest take on when not to use it.
Why Patterns Still Matter in Python
Python lets you implement the same thing six different ways. That's a feature until you're on a team, then it's a coordination problem.
