Eric V. Smith <e...@trueblade.com> added the comment:
The more I think about this, the more I think it shouldn't be in the stdlib.
paul.j3 is correct that the simple case is just type=pathlib.Path.
For something more adventurous you could start with:
@dataclass(eq=True, frozen=True)
class ArgumentPath:
must_exist: bool = False
# Add other conditions as needed.
def __call__(self, val):
result = Path(val)
if self.must_exist:
if not result.exists():
raise ValueError(f"path {result} must exist")
return result
The reason I think this shouldn't be in the stdlib is that there are race
conditions here between when you inspect the filesystem and when you'd actually
use the path. What if the file was deleting, or it went from being a directory
to a file?
I think the best advice is to use type=pathlib.Path, and handle anything else
when you try to cd, or open, or whatever it is you're doing with the path.
It probably wouldn't hurt to document type=pathlib.Path in the argparse docs.
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<https://bugs.python.org/issue42572>
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