Comment by lexicality

One thing that post does do though is very clearly highlight the difference between Python's type system and say ... TypeScript's.

TypeScript's goal is to take a language with an unhinged duck type system that allows people to do terrible things and then allow you to codify and lock in all of those behaviours exactly as they're used.

Mypy (and since it was written by GVM and codified in the stdlib by extension Python and all other typecheckers)'s goal is to take a language with an unhinged duck type system that allows people to do terrible things and then pretend that isn't the case and enforce strict academic rules and behaviours that don't particularly care about how real people write code and interact with libraries.

If you include type hints from the very beginning than you are forced to use the very limited subset of behaviours that mypy allow you to codify and everything will be "fine".

If you try to add type hints to a mature project, you will scream with frustration as you discover how many parts of the codebase literally cannot be represented in the extremely limited type system.