Python

I only use it to avoid circular imports. Otherwise, I can import the type plainly.

I don’t like having to quote the types, so I use it exclusively for avoiding circular imports.

That's a very cool feature, had no clue about it!

If it doesn't have any visible downsides, it's be nice use it whenever possible. This should provide the additional benefit of having the imports clearly separated.

The tediousness aspect of it makes me wonder though. I'd probably just only use it when I'm specifically importing something only for typing .

Maybe could be a cool feature request for an lsp as well.

Any time you need different behavior between static type checking and runtime.

in 3.10 I’m using it to work around issue with NamedTuple generics. typing_extensions.NamedTuple allows Generics at runtime but typing.NamedTuple doesn’t. But the type checker we are using doesn’t support typing_extensions.NamedTuple like it does for the typing version so we lie at type checking time to get the typing to make sense but have different runtime type because otherwise its a TypeError

A cheeky answer: whenever Ruff/flake8-type-checking tells me to. Though I'd only enable that check now that there's an autofix in Ruff as well.

You should have part of your test harness perform a separate import of every module. If your module is idempotent (most good code is) you could do this in a single process by cleaning sys.modules I guess ... but it still won't be part of your pytest process.

Static analyzers can only detect some cases, so can't be fully trusted.

I've also found there are a lot of cases where performant Python code has to be implemented in a distinct way from what the type-checker sees. You can do this with aggressive type: ignore but I often find it cleaner to use separate if blocks.