I am using django multi-table inheritance: Video and Image are models derived from Media. I have implemented two views: video_list and image_list, which are just proxies to media_list. media_list returns images or videos (based on input parameter model) for a certain object, which can be of type Event, Member, or Crag. It alters its behaviour based on input parameter action, which can be either "edit" or "view".

The problem is that I need to ask whether the input parameter model contains Video or Image in media_list so that I can do the right thing. Similar condition is also in helper method media_edit_list that is called from the view.

I don't particularly like it but the only alternative I can think of is to have separate logic for video_list and image_list and then probably also separate helper methods for videos and images: video_edit_list, image_edit_list, video_view_list, image_view_list. So four functions instead of just two. That I like even less because the video functions would be very similar to the respective image functions. What do you recommend?

Here is extract of relevant parts: http://pastebin.com/07t4bdza. I'll also paste the code here:

#urls
      url(r'^media/images/(?P<rel_model_tag>(event|member|crag))/(?P<rel_object_id>\d+)/(?P<action>(view|edit))/$', views.video_list, name='image-list')
      url(r'^media/videos/(?P<rel_model_tag>(event|member|crag))/(?P<rel_object_id>\d+)/(?P<action>(view|edit))/$', views.image_list, name='video-list')




#views
def image_list(request, rel_model_tag, rel_object_id, action):
    return media_list(request, Image, rel_model_tag, rel_object_id, action)


def video_list(request, rel_model_tag, rel_object_id, action):
    return media_list(request, Video, rel_model_tag, rel_object_id, action)


def media_list(request, model, rel_model_tag, rel_object_id, action):
    rel_model = tag_to_model(rel_model_tag)
    rel_object = get_object_or_404(rel_model, pk=rel_object_id)

    if model == Image:
        star_media = rel_object.star_image
    else:
        star_media = rel_object.star_video

    filter_params = {}
    if rel_model == Event:
        filter_params['media__event'] = rel_object_id
    elif rel_model == Member:
        filter_params['media__members'] = rel_object_id
    elif rel_model == Crag:
        filter_params['media__crag'] = rel_object_id

    media_list = model.objects.filter(~Q(id=star_media.id)).filter(**filter_params).order_by('media__date_added').all()

    context = {
        'media_list': media_list,
        'star_media': star_media,
    }

    if action == 'edit':
        return media_edit_list(request, model, rel_model_tag, rel_model_id, context)

    return media_view_list(request, model, rel_model_tag, rel_model_id, context)


def media_view_list(request, model, rel_model_tag, rel_object_id, context):
    if request.is_ajax():
        context['base_template'] = 'boxes/base-lite.html'
    return render(request, 'media/list-items.html', context)


def media_edit_list(request, model, rel_model_tag, rel_object_id, context):
    if model == Image:
        get_media_record = get_image_record
    else:
        get_media_record = get_video_record

    media_list = [get_media_record(media, rel_model_tag, rel_object_id) for media in context['media_list']]

    if context['star_media']:
        star_media = get_media_record(star_media, rel_model_tag, rel_object_id)
        star_media['starred'] = True
    else:
        star_media = None

    json = simplejson.dumps({
        'star_media': star_media,
        'media_list': media_list,
    })
    return HttpResponse(json, content_type=json_response_mimetype(request))




# models
class Media(models.Model, WebModel):
    title = models.CharField('title', max_length=128, default='', db_index=True, blank=True)
    event = models.ForeignKey(Event, null=True, default=None, blank=True)
    crag = models.ForeignKey(Crag, null=True, default=None, blank=True)
    members = models.ManyToManyField(Member, blank=True)
    added_by = models.ForeignKey(Member, related_name='added_images')
    date_added = models.DateTimeField('date added', auto_now_add=True, null=True, default=None, editable=False)

    def __unicode__(self):
        return self.title

    def get_absolute_url(self):
        return self.image.url if self.image else self.video.embed_url


class Image(Media):
    image = ProcessedImageField(upload_to='uploads',
                                processors=[ResizeToFit(width=1024, height=1024, upscale=False)],
                                format='JPEG',
                                options={'quality': 75})
    thumbnail_1 = ImageSpecField(source='image',
                                processors=[SmartResize(width=178, height=134)],
                                format='JPEG',
                                options={'quality': 75})
    thumbnail_2 = ImageSpecField(source='image',
                                #processors=[SmartResize(width=256, height=192)],
                                processors=[ResizeToFit(height=164)],
                                format='JPEG',
                                options={'quality': 75})


class Video(Media):
    url = models.URLField('url', max_length=256, default='')
    embed_url = models.URLField('embed url', max_length=256, default='', blank=True)
    author = models.CharField('author', max_length=64, default='', blank=True)
    thumbnail = ProcessedImageField(upload_to='uploads',
                                processors=[ResizeToFit(width=1024, height=1024, upscale=False)],
                                format='JPEG',
                                options={'quality': 75}, null=True, default=None, blank=True)
    thumbnail_1 = ImageSpecField(source='thumbnail',
                                processors=[SmartResize(width=178, height=134)],
                                format='JPEG',
                                options={'quality': 75})
    thumbnail_2 = ImageSpecField(source='thumbnail',
                                #processors=[SmartResize(width=256, height=192)],
                                processors=[ResizeToFit(height=164)],
                                format='JPEG',
                                options={'quality': 75})

  class Crag(models.Model, WebModel):
      name = models.CharField('name', max_length=64, default='', db_index=True)
      normalized_name = models.CharField('normalized name', max_length=64, default='', editable=False)
      type = models.IntegerField('crag type', null=True, default=None, choices=crag_types)
      description = models.TextField('description', default='', blank=True)
      country = models.ForeignKey('country', null=True, default=None) #TODO: make this not null when db enables it
      latitude = models.FloatField('latitude', null=True, default=None)
      longitude = models.FloatField('longitude', null=True, default=None)
      location_index = FixedCharField('location index', length=24, default='', editable=False, db_index=True) # handled by db, used for marker clustering
      added_by = models.ForeignKey('member', null=True, default=None)
      #route_count = models.IntegerField('route count', null=True, default=None, editable=False)
      date_created = models.DateTimeField('date created', auto_now_add=True, null=True, default=None, editable=False)
      last_modified = models.DateTimeField('last modified', auto_now=True, null=True, default=None, editable=False)
      star_image = models.OneToOneField('Image', null=True, default=None, related_name='star_crags', on_delete=models.SET_NULL)
      star_video = models.OneToOneField('Video', null=True, default=None, related_name='star_crags', on_delete=models.SET_NULL)