[jameshart]

Inheritance is only good for code reuse, and it’s a trick you only get to use once for each piece of code, so if you use it you need to be absolutely certain that the taxonomy you’re using it to leverage code across is the right one.

All ‘is-a so it gets this code’ models can be trivially modeled as ‘has-a so it gets this code’ patterns, which don’t have that single-use constraint… so the corollary to this rule tends towards ‘never use inheritance’.

[Spivak]

Single use? No way that's what multiple inheritance and mixins are for. Inheritance being only for code reuse is explicitly about not creating a taxonomy. No more is-a just, "I need this code here." Hey this thing behaves like a mapping inherit from the MutipleMapping and get all the usual mapping methods for free. Hey this model needs created/updated_at, inherit from ChangeTracking and get those fields and helper methods for free.

Has-a doesn't make sense for code like the literal text reuse. It makes sense for composition and encapsulation.

Edit: I'm now realizing that Python has one of the only sane multiple inheritance implementations. It's no wonder the rest of y'all hate it.