Feature request: separate TYPE_CHECKING

[juanolon]

Hello,
I was looking for a option to separate my imports, which are only for type checking from all the others, and wrap them into an if block. I look into the issues and only found this thread: #818 (comment)

It would convert this:

from torch.utils.data.dataset import Dataset
from argparse import ArgumentParser
import torch

to

if TYPE_CHECKING:
    from torch.utils.data.dataset import Dataset

from argparse import ArgumentParser
import torch

That would be huge. Thanks!

[timothycrosley]

Hi @juanolon,

I can see why this would be useful, but unfortunately, while it may seem simple on the outside, it goes well behind what isort could reasonably support. isort only looks at, parses, and understands imports. This would require it to fully understand all syntax elements to even get it right most of the time. Even if it did that, it would still fail plenty of times, where either the import has a side effect that's intentional, or the annotation is meant for runtime (ala fastapi).

Sorry!

~Timothy

[juanolon]

ic. thanks anyway!

[NeilGirdhar]

@timothycrosley Any chance you could revisit this now that a flake8 plugin suggests putting things under type checking blocks? We would only need to support if TYPE_CHECKING, and no other constructs.

[henzef]

It would be great if you could reconsider implementing this @timothycrosley. I think "require it to fully understand all syntax elements" is a bit overestimated here, because this would just need a single special case for "if TYPE_CHECKING".
The combination with the flake8 plugin as proposed by @NeilGirdhar would indeed be awesome to have!

Please also note that even mypys own detection of this is extremely simple. it doesnt even support import aliases: python/mypy#12928