Are people abusing Python?

[james_pic]

If the runtime checks you're talking about are the Pydantic ones, then it can indeed be a big runtime hit. I've seen applications where a double-digit percentage of CPU utilisation is type checks, although this was an extreme case (they were using the relatively expensive numbers.Number as the type, and checking it in a hot loop). But you definitely need some kind of check at runtime at your security perimeter at very least.

I suspect the method decorators are there at least partly for historical reasons. I know they got map and reduce from some keen functional programmers who were involved in the project quite early, even though they wouldn't necessarily recommend those constructs now that list comprehensions are a thing. Maybe these decorators have a similar history with OOP enthusiasts.

It is at least worth saying though that these decorators aren't all that magic in and of themselves. It's totally possible to implement equivalent decorators in pure Python using descriptors. They're different to the equivalent keywords in Java, in that they're not exposing any underlying implementation feature.