How to use "--" as an argument in python argparser

Question

I have the following python code set up, in which the program would return "something" whenever the user pass -- as an argument:

#script.py

import argparse

parser = argparse.ArgumentParser()

parser.add_argument(
    "--",
    help="Prints something",
    action="store_true",
    dest="print_something",
)

args = parser.parse_args()

if args.print_something:
    print("something")

The output is as follows:

$ python .\script.py --

usage: script.py [-h] [--]
playground.py: error: unrecognized arguments: --

Argparse is not able to recognise the -- argument.

I tried using escape sequences, like putting -\-\- under parser.add_argument(, yet the program is not behaving the way it should.

There is, of course, a workaround using sys.arg, which goes something like:

import sys

if "--" in sys.argv:
    print("something")

But the above approach is impractical for projects with alot of arguments -- especially for those containing both functional and positional argument.

Therefore, is there anyway to parse the -- argument using argparser?

That's a weird thing to want. -- conventionally has a very specific meaning. In isolation, you don't seem to need an option at all; if the program doesn't do anything without the option, it's not optional. — tripleee
– tripleee, Commented Aug 26, 2024 at 11:24
"is there anyway to parse the -- argument using argparser?" I'm going to say "no", since argparse will consider the use of -- having a special meaning, namely "end of options". It's unconvential, probably unwise, and likely impossible, to override that behaviour. — 9769953
– 9769953, Commented Aug 26, 2024 at 11:54

DanielL · Accepted Answer · 2024-08-26 12:25:45Z

1

Not sure if this is what you mean, but using this logic you can detect -- and process other using something like this:

import argparse

parser = argparse.ArgumentParser()

# Define a positional argument to capture `--` and any arguments after it
parser.add_argument(
    'args',
    nargs=argparse.REMAINDER,
    help="Arguments after --"
)

parsed_args = parser.parse_args()

# Check if `--` is in the arguments
if '--' in parsed_args.args:
    print("Found -- in arguments")
    # You can process the arguments after `--` here
    remaining_args = parsed_args.args[parsed_args.args.index('--') + 1:]
    # process other arguments here
    print("Arguments after --:", remaining_args)
else:
    print("No -- found in arguments")

So to answer your question: yes, but its quite niche.

answered Aug 26, 2024 at 12:25

DanielL

2421 silver badge10 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Epimu Salon Over a year ago

I see, using the nargs=argparse.REMAINDER approach is just great and intuitive. Just what I wanted. Thanks!

DanielL Over a year ago

glad to be of help!

Collectives™ on Stack Overflow

How to use "--" as an argument in python argparser

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related