So far I'm working it into personal projects gradually. Runtime checks are at least as useful as something like pydantic's validation, and more expressive, because validation is basically "pre" but now deal can provide the "post". DBC via pre/post might be "just" syntactic sugar on asserts, but notation matters: it looks great, it reduces cognitive load. It easily does stuff that's impossible or just awkward with types, so having an alternate way to express constraints available probably keeps me out of certain rabbit holes.

Really looking forward to trying verification ( https://deal.readthedocs.io/basic/verification.html ) but I think I need to hit some critical mass of annotation first.