Gfrktyl

I was wondering if there was a better way to implement my cli parser.

For context:
I need to pass to my script either a file in one of two formats or two files in a specific format.

It may be easier to understand like this:

file.ext1 OR file.ext2 OR (file_1.ext2 AND file_2.ext2)

I've used python argparse add_mutually_exclusive_group successfully and it looks like this:

import argparse

parser = argparse.ArgumentParser()

group = parser.add_mutually_exclusive_group(required=True)

group.add_argument(

    "--ext1",

    type    = __existant_file,

    metavar = "FILE",

    help    = "input file (format ext1)"

)

group.add_argument(

    "--ext2",

    type    = __existant_file,

    metavar = "FILE",

    help    = "input file (format ext2)"

)

group.add_argument(

    "--paired",

    nargs   = 2,

    type    = __existant_file,

    metavar = ("MATE_1", "MATE_2"),

    help    = "input file (two files format ext2)"

)



args = parser.parse_args()

print(args)



if args.ext1 is not None:

  file = args.ext1

elif args.ext2 is not None:

  file = args2.ext2

else:

  file = args.paired[0]

  file2 = args.paired[1]

Which is used as:

python script.py --ext1 file

OR

python script.py --ext2 file

OR

python script.py --paired file_1 file_2

Which is working but not really smooth. Do you have any lead of how I can improve the CLI parser ?

Okay, I found a better way

import argparse

parser = argparse.ArgumentParser()



class RequiredLen(argparse.Action):

        def __call__(self, parser, args, values, option_string=None):

            if not 1 <= len(values) <= 2:

                msg = f"argument {self.dest} requires 1 or 2 arguments"

                raise argparse.ArgumentTypeError(msg)

            setattr(args, self.dest, values)

# Just give me 1 or 2 files

parser.add_argument(

    "--paired",

    nargs    = '+',

    action   = RequiredLen,

    required = True,

    help     = "input file(s)"

)

# Specify either ext1 or ext2 format

group = parser.add_mutually_exclusive_group(required=True)

group.add_argument(

    "--ext1",

    action = "store_const",

    dest   = "format",

    const  = "ext1",

    help   = "input is ext1 format"

)

group.add_argument(

    "--ext2",

    action = "store_const",

    dest   = "format",

    const  = "ext2",

    help   = "input is ext2 format"

)

args = parser.parse_args()

print(args)

This way I can later just use something like:

def process_ext1(l: list):

   print("ext1 file(s)")

   for i in l:

       print(i)



def process_ext2(l: list):

   print("ext2 file(s)")

   for i in l:

       print(i)



process_format = { 'ext1': process_ext1, 'ext2': process_ext2 }

process_format[args.format](args.paired)