Datasette currently has a few API internals that return sqlite3.Row objects. I was thinking about how this might work in the future - if Datasette ever expands beyond SQLite (plugin-provided backends for PostgreSQL and DuckDB for example) I'd want a way to return data from other stores using objects that behave like sqlite3.Row but are not exactly that class.
I’m not complaining, just reflecting that it is weird to me. The static type checker is almost an admission that type checking is a Good Thing, but Python continues to resist adding runtime checking. Modules like typing and Protocol don’t seem to do anything at runtime, and because of that are deeply weird to me - what kind of include doesn’t have runtime code? I haven’t seen anything quite like it in any other language I’ve coded in. It just seems included for the coders’ IDE to throw warnings, and that’s it.
Then again, it’s entirely possible I just don’t get around much. I’m not a software guy, I’m hardware, and occasionally I’ll write a tool or website to help with a specific task.
I suppose the alternative is just as weird or weirder, where there are almost two separate languages, one strongly typed and one not typed at all.
How would they add runtime checking without breaking all existing code?
But I think warning people is a good start, because those checks can be added to your CI pipeline and reject any incoming code that contains warnings. That way you can enforce type checking for a subset of modules and keep backwards compatibility.
By making it opt-in. But that’s not much different from static typing then, except that it won’t actually work when you screw up typing