from collections import namedtuple

from django.db.models import *


def _get_field_choices(named):
    """
    Namedtuple expected, return Django field choices
    """
    dictionary = named._asdict()
    return [(v, k) for (k, v) in dictionary.items()]

def get_named_choices(name, choices):
    choices = namedtuple(name, choices)(*range(len(choices)))
    return _get_field_choices(choices)


class Photo(Model):
    _image_types = {
        'COLOUR' : 0, 
        'BLACKWHITE' : 1, 
        'MONOCHROME' : 2, 
        'UNKNOWN' : 9, 
    }
    IMAGE_TYPE = get_named_choices('ImageType', _image_types)

    image_type = PositiveSmallIntegerField(
        default=0,
        choices=get_field_choices(IMAGE_TYPE)
    )

"""
usage: myphoto.image_type = Photo.IMAGE_TYPE.BLACKWHITE
"""