[Python-Dev] PEP 389: argparse - new command line parsing module

[Steven Bethard]

On Mon, Sep 28, 2009 at 12:22 PM, Brett Cannon <brett at python.org> wrote:
> On Mon, Sep 28, 2009 at 08:49, Steven Bethard <steven.bethard at gmail.com> wrote:
>> On Mon, Sep 28, 2009 at 8:27 AM, Steven D'Aprano <steve at pearwood.info> wrote:
>>> On Tue, 29 Sep 2009 12:28:39 am Steven Bethard wrote:
>>>> * Would you like argparse to grow an add_getopt_arguments method (as
>>>> in my other post)?
>>>
>>> 0
>>>
>>>> * If argparse grew an add_getopt_arguments, would you still want to
>>>> keep getopt around? And if so, why?
>>>
>>> Simplicity of the learning curve. Using it is as simple as:
>>>
>>> getopt.getopt(sys.argv[1:], "a:b", ["alpha=", "beta"])
>>
>> You forgot the for-loop, nested if/else statements and type conversions. ;-)
>>
>
> =) I do wonder if people who are advocating for getopt sticking around
> realize how much extra code must be written to make sure what it gives
> back to you is in some sane manner.
>
> Let's take ``getopt.getopt(sys.argv[1:], "a:b", ["alpha=", "beta"])``
> as an example and simply assume that 'alpha' takes a string as an
> argument and that it's required and that 'beta' is a boolean flag. To
> pull everything out you could do::
>
>  options, args = getopt.getopt(sys.argv[1:], "a:b", ["alpha=", "beta"])
>  options_dict = dict(options)
>  alpha = options_dict.get('-a', options_dict.get('--alpha', ''))
>  beta = '-b' in options_dict or '--beta' in options_dict
>
>  main(alpha, beta, args)
>
> Obviously if one of the getopt supporters has a better way of doing
> this then please speak up.
>
> Now, Steven, can you show how best to do this in argparse?

Here's the same option parsing in argparse:

    parser = argparse.ArgumentParser()
    parser.add_argument('-a', '--alpha')
    parser.add_argument('-b', '--beta', action='store_true')
    args = parser.parse_args()

    main(args.alpha, args.beta)

Or if those final positional arguments were actually meaningful, then
you would add one more argument like this::

    parser = argparse.ArgumentParser()
    parser.add_argument('-a', '--alpha')
    parser.add_argument('-b', '--beta', action='store_true')
    parser.add_argument('gammas', nargs='*')
    args = parser.parse_args()

    main(args.alpha, args.beta, args.gammas)

Steve
-- 
Where did you get that preposterous hypothesis?
Did Steve tell you that?
        --- The Hiphopopotamus