argparse csv + choices

[Robert Kern]

On 3/30/11 10:32 AM, Neal Becker wrote:
> I'm trying to combine 'choices' with a comma-seperated list of options, so I
> could do e.g.,
>
> --cheat=a,b
>
>      parser.add_argument ('--cheat', choices=('a','b','c'), type=lambda x:
> x.split(','), default=[])
>
> test.py --cheat a
>   error: argument --cheat: invalid choice: ['a'] (choose from 'a', 'b', 'c')
>
> The validation of choice is failing, because parse returns a list, not an item.
> Suggestions?

Do the validation in the type function.


import argparse

class ChoiceList(object):
     def __init__(self, choices):
         self.choices = choices

     def __repr__(self):
         return '%s(%r)' % (type(self).__name__, self.choices)

     def __call__(self, csv):
         args = csv.split(',')
         remainder = sorted(set(args) - set(self.choices))
         if remainder:
             raise ValueError("invalid choices: %r (choose from %r)" % 
(remainder, self.choices))
         return args


parser = argparse.ArgumentParser()
parser.add_argument('--cheat', type=ChoiceList(['a','b','c']), default=[])
print parser.parse_args(['--cheat=a,b'])
parser.parse_args(['--cheat=a,b,d'])

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
  that is made terrible by our own mad attempt to interpret it as though it had
  an underlying truth."
   -- Umberto Eco