Arbitrary command line arguments in python

Question

I want to allow arbitrary command line arguments. If the user provides me with a command line that looks like this

myscript.py --a valueofa --b valueofb posarg1 posarg2

I know that a was passed with valueofa, b passed with valueofb and that I have these last two positional arguments.

I've always used optparse, for which you specify exactly which arguments to look for. But I want the user to be able to define arbitrary "macros" from the command line. Surely there's a python module that does it more elegantly than anything I'd write. What is?

The analogy I had in mind was using gcc like -Dthismacro=macrovalue — pythonic metaphor
– pythonic metaphor, Commented Jul 28, 2010 at 20:02

Sergey Nagaytsev · Accepted Answer · 2015-10-06 10:35:24Z

4

arbitrary_args.py:

#!/usr/bin/env python3

import sys


def parse_args_any(args):
    pos = []
    named = {}
    key = None
    for arg in args:
        if key:
            if arg.startswith('--'):
                named[key] = True
                key = arg[2:]
            else:
                named[key] = arg
                key = None
        elif arg.startswith('--'):
            key = arg[2:]
        else:
            pos.append(arg)
    if key:
        named[key] = True
    return (pos, named)


def main(argv):
    print(parse_args_any(argv))


if __name__ == '__main__':
    sys.exit(main(sys.argv[1:]))

$./arbitrary_args.py cmd posarg1 posarg2 --foo --bar baz posarg3 --quux:

(['cmd', 'posarg1', 'posarg2', 'posarg3'], {'foo': True, 'bar': 'baz', 'quux': True})

argparse_arbitrary.py:

#!/usr/bin/env python3
import argparse
parser = argparse.ArgumentParser()
parser.add_argument('-D', action='append', )
D = {L[0]:L[1] for L in [s.split('=') for s in parser.parse_args().D]}
print(D)

$./argparse_arbitrary.py -Ddrink=coffee -Dsnack=peanut

{'snack': 'peanut', 'drink': 'coffee'}

answered Oct 6, 2015 at 10:35

Sergey Nagaytsev

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1 Comment

Zheng Liu Over a year ago

I think this should be selected as the best answer.

Community · Accepted Answer · 2017-05-23 11:44:29Z

2

Sadly, you can't. If you have to support this, you'll need to write your own option parser =(.

edited May 23, 2017 at 11:44

CommunityBot

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answered Jul 28, 2010 at 19:29

Katriel

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Comments

ʇsәɹoɈ · Accepted Answer · 2010-07-28 19:31:49Z

0

Will argparse do what you want? It was recently added to the standard library. Specifically, you might want to look at this section of the documentation.

answered Jul 28, 2010 at 19:31

ʇsәɹoɈ

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1 Comment

Katriel Over a year ago

I think it doesn't: "The parse_args method attempts to give errors whenever the user has clearly made a mistake" means that undefined arguments will cause errors. In fact, I think this is deliberate behaviour -- it's not often that you want to allow e.g. spelling mistakes.

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