[stdlib] Add a comment to the alias for the return type of urllib.request.urlopen

[edgarrmondragon]

No description provided.

[srittau]

Unfortunately, this would require every user of urlopen() to add a cast or isinstance check, so it's not feasible to change this. But it's a case where python/typing#566 would be useful. That said, we should add an appropriate comment to the type var, explaining the expected return types.

[edgarrmondragon]

Unfortunately, this would require every user of urlopen() to add a cast or isinstance check, so it's not feasible to change this. But it's a case where python/typing#566 would be useful.

Thanks @srittau, I see that now. Even in my own code which motivated this change, I'd need to add a type assertion to make it actually work after this change.

That said, we should add an appropriate comment to the type var, explaining the expected return types.

You mean to _UrlopenRet?

[srittau]

You mean to _UrlopenRet?

Yes. If you want to, you can change this PR accordingly. Otherwise, I'll add a comment.

[edgarrmondragon]

Yes. If you want to, you can change this PR accordingly. Otherwise, I'll add a comment.

I'll do that

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉

[srittau]

Thanks!