argparse action or type for comma-separated list

Question

I want to create a command line flag that can be used as

./prog.py --myarg=abcd,e,fg

and inside the parser have this be turned into ['abcd', 'e', 'fg'] (a tuple would be fine too).

I have done this successfully using action and type, but I feel like one is likely an abuse of the system or missing corner cases, while the other is right. However, I don't know which is which.

With action:

import argparse

class SplitArgs(argparse.Action):
    def __call__(self, parser, namespace, values, option_string=None):
        setattr(namespace, self.dest, values.split(','))


parser = argparse.ArgumentParser()
parser.add_argument('--myarg', action=SplitArgs)
args = parser.parse_args()
print(args.myarg)

Instead with type:

import argparse

def list_str(values):
    return values.split(',')

parser = argparse.ArgumentParser()
parser.add_argument('--myarg', type=list_str)
args = parser.parse_args()
print(args.myarg)

Answer 1

The simplest solution is to consider your argument as a string and split.

#!/usr/bin/env python3

import argparse

parser = argparse.ArgumentParser()
parser.add_argument("--myarg", type=str)
d = vars(parser.parse_args())
if "myarg" in d.keys():
    d["myarg"] = [s.strip() for s in d["myarg"].split(",")]
print(d)

Result:

$ ./toto.py --myarg=abcd,e,fg
{'myarg': ['abcd', 'e', 'fg']}
$ ./toto.py --myarg="abcd, e, fg"
{'myarg': ['abcd', 'e', 'fg']}