Absl flags pathlib support

[bsarden]

Are there any plans to support a flags.DEFINE_path or something similar that utilizes python's pathlib module to support declaring os.PathLike operations for the default option?

For context, I often find myself doing the following:

from absl import app, flags
from pathlib import Path

FLAGS = flags.FLAGS
flags.DEFINE_string("filepath", "path/to/some.txt", "Input filepath for program")

def main(argv_):
    # Override FLAGS.filepath with a pathlib.Path version
    FLAGS.filepath = Path(FLAGS.filepath)
    
    # Rest of program uses pathlib for path operations

if __name__ == "__main__":
    app.run(main)

It would be awesome if there was an easy way to define a Path object from the DEFINE_ definition in the first place. If adding such a feature is not feasible, I'm curious how other people are using pathlib with absl.flags as well.

Thanks!

[gpshead]

Internally I do see one recent user contributed library that implements its own DEFINE_path for use with absl. The gist of that goes something like this (simplified for illustration purposes) in apath_flag.py library:

flags.disclaim_key_flags()  # Prevent absl from attributing flags to this module.

class _PathParser(flags.ArgumentParser):
    def parse(self, value):
        return pathlib.PurePath(value)

class _PathSerializer(flags.ArgumentSerializer):
    def serialize(self, value):
        return str(value)

def DEFINE_path(...):
    return flags.DEFINE(_PathParser(), name, default, help, flag_values,
                        _PathSerializer(), **kwargs)

I agree, it'd make sense to add something like that to absl itself as pathlib is gaining popularity.

Internal source: pyglib.contrib.gpathlib - If we do this, presumably we might just refactor it out of that.

[danielkelshaw]

Just wondering if there was any update on this? I'd say the pathlib library is fairly standard now so it would be nice to have support from absl if possible.

[yilei]

Yes this is in my queue, hopefully I can get to it after the holidays if not earlier.

[aryamccarthy]

Perhaps DEFINE_path can happen by these holidays? :-)