Having options in argparse with a dash

Question

I want to have some options in argparse module such as --pm-export however when I try to use it like args.pm-export I get the error that there is not attribute pm. How can I get around this issue? Is it possible to have - in command line options?

Asked By: Cemre Mengü

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Source

Answer 1

Dashes are converted to underscores:

import argparse
pa = argparse.ArgumentParser()
pa.add_argument('--foo-bar')
args = pa.parse_args(['--foo-bar', '24'])
print args # Namespace(foo_bar='24')

Answered By: georg

Answer 2

As indicated in the argparse docs:

For optional argument actions, the value of dest is normally inferred from the option strings. ArgumentParser generates the value of dest by taking the first long option string and stripping away the initial -- string. Any internal - characters will be converted to _ characters to make sure the string is a valid attribute name

So you should be using args.pm_export.

Answered By: Thomas Orozco

Answer 3

Unfortunately, dash-to-underscore replacement doesn’t work for positional arguments (not prefixed by --).
E.g:

parser = argparse.ArgumentParser(description='Process some integers.')
parser.add_argument('logs-dir',
                    help='Directory with .log and .log.gz files')
parser.add_argument('results-csv', type=argparse.FileType('w'),
                    default=sys.stdout,
                    help='Output .csv filename')
args = parser.parse_args()
print args

# gives
# Namespace(logs-dir='./', results-csv=<open file 'lool.csv', mode 'w' at 0x9020650>)

So, you should use 1’st argument to add_argument() as attribute name and metavar kwarg to set how it should look in help:

parser = argparse.ArgumentParser(description='Process some integers.')
parser.add_argument('logs_dir', metavar='logs-dir',
                    nargs=1,
                    help='Directory with .log and .log.gz files')
parser.add_argument('results_csv', metavar='results-csv',
                    nargs=1,
                    type=argparse.FileType('w'),
                    default=sys.stdout,
                    help='Output .csv filename')
args = parser.parse_args()
print args

# gives
# Namespace(logs_dir=['./'], results_csv=[<open file 'lool.csv', mode 'w' at 0xb71385f8>])

Answered By: seriyPS

Answer 4

getattr(args, 'positional-arg')

This is another OK workaround for positional arguments:

#!/usr/bin/env python3

import argparse

parser = argparse.ArgumentParser()
parser.add_argument('a-b')
args = parser.parse_args(['123'])
assert getattr(args, 'a-b') == '123'

Tested on Python 3.8.2.

Answered By: Ciro Santilli OurBigBook.com

Answer 5

Concise and explicit but probably not always acceptable way would be to use vars():

#!/usr/bin/env python3

import argparse

parser = argparse.ArgumentParser()
parser.add_argument('a-b')
args = vars(parser.parse_args())

print(args['a-b'])

Answered By: Denis The Menace

Answer 6

I guess the last option is to change shorten option -a to --a

import argparse

parser = argparse.ArgumentParser(description="Help")
parser.add_argument("--a", "--argument-option", metavar="", help="")   # change here
args = parser.parse_args()
option = args.a                # And here
print(option)

Answered By: Dang Max

Having options in argparse with a dash

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