Django. Confusing query. Count items

I have table cold Mark.

class Mark(models.Model):
    media = models.ForeignKey('media.Media')
    mark = models.PositiveIntegerField()
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    class Meta:
        unique_together = ('media_object','user')

How can i get query set of media instances (or just count the media) which has at least one vote?

Can i make it whith out using extra?

UPDATED: I other words: I'm running through all table and counting all unique media. If i found it second time I'm not counting it. Other words: I need count unique media fields.

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I'm assuming the "Mark" model is how users vote. To get all media models with their mark counts, you need aggregation:

from django.db.models import Count

media_with_vote_count = Media.objects.annotate(vote_count=Count('mark_set'))

You can then use filter() that refers to that annotation:

voted_media = media_with_vote_count.filter(vote_count__gt=0)

There are also other useful aggregates. For example, you could calculate an average mark for every media:

from django.db.models import Avg

media_with_markavg = Media.objects.annotate(average_mark=Avg('mark_set__mark'))

---

    mk = Mark.objects.all()
    mk.media.count()

U can use the count function but not sure of ur question what u want to do from it or what is vote..

EDIT:

          One row of media

          if( mk.media.count() > 0):
                    ......