Is it possible to use argparse for passing optional arguments without the dash symbol?

Question

I have a program which can take in a few different arguments, and depending on what the argument is that is passed, that function is called in the python program. I know how to use sys.arv, and I have used argparse before, however I am not sure how to go about accomplishing the following with argparse..

Possible arguments: func1, func2, func3

Program could be executed with either of the following:

python myprogram func1
python myprogram func2
python myprogram func3

Therefore the arg passed correlates to a function in the program. I do not want to include any dashes in the arguments so nothing like -func1 or -func2...etc.

Thank you!

hpaulj · Accepted Answer · 2016-09-11 22:44:26Z

1

 parser.add_argument('foo', choices=['func1','func2','func3'])

will accept one string, and raise an error if that string is not one of the chocies. The results will be a namespace like

 Namespace(foo='func1')

and

 print(args.foo)
 # 'func1'

Is that what you want?

The subparsers mechanism does the same thing, but also lets you define added arguents that can differ depending on which subparser is given.

answered Sep 11, 2016 at 22:44

hpaulj

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7 Comments

Jane Doe Over a year ago

Yes, that was much simpler than I originally thought it would be. Thank you!

Jane Doe Over a year ago

Just one question...How can I make a call to the function based on the arg that was passed? Something like args.foo() or foo() ?

hpaulj Over a year ago

You have to match the string with the function, for example with a dictionary. dd = {'func1':func1, 'func2':func2}; dd[args.foo](). The docs describes a different mechanism when using subparsers (using setdefault).

Jane Doe Over a year ago

Awesome, that makes sense. Thank you!

Steve Jessop Over a year ago

Alternatively if the functions are in a module called module then you could call it as getattr(module, args.foo)(). Normally you don't like to look up code in a module using user input, because they could type anything, but in this case you've explicitly constrained their choices already so it's not so bad. If the functions are in the current module you can get it as sys.modules[__name__], or do globals()[args.foo].

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