imports+two lines of code is a risk of raising a new exception. You may do that before and use the path to load the resource. I'm not sure.

Is it possible that tzdata is in a ZIP file, or in memory but not on disk?

Maybe it's overcomplicated and maybe it's better to convertany OSError into a ZoneInfoNotFoundError. I let@pganssle decides what is the best.

Yeah, I don't like this at all. Inimportlib_resources there's a way to determine if something is a directory or not using theimportlib.resources.files API.

That will complicate things a bit for the backport, though, which doesn't currently requireimportlib_resources in Python 3.8.

I'm inclined to go the simple way and catchallOSErrors instead of the more narrowly scoped ones. I realize this may frustrate some people debugging in unusual environments by disguising the source of some errors, but I don't love that the standardZoneInfo constructor is exposing details about the specifics of the underlying file system.

@jaraco Do you know if there's an equivalent ofimportlib.resources.files('my.package').joinpath('resource').isdir() that works for Python 3.8's version ofimportlib.resources?

In Python 3.8 and earlier,importlib.resources didn't support directories as resources - all resources were required to be files directly in a package.

@jaraco Well, we're not really concerned with using a directory as a resource, the problem is that it appears thatimportlib.resources raisesPermissionError on Windows when a directory is specified, and we're trying to distinguish between the case where a purported resourceexists but is a directory and the case of a legitimate permissions error.

Is there no way to do that in the Python 3.8importlib.resources?

swapped to usingimportlib.resources.files to locate the resource however inclined to agree that catching all OSError derivatives might prove less problematic.

@pganssle Apologies for having dropped the ball on this one.

I don't believe there's a reliable in the older importlib.resources API to detect that a directory is present. It was meant to be the case that a directory was indistinguishable from 'not a resource'.

What I would recommend though is to useimportlib.resources here, but in the zoneinfo backport, useimportlib_resources, which implements thefiles() API even on Python 2.