Suppose I have something like this in my models.py:
class Hipster(models.Model): name = CharField(max_length=50) class Party(models.Model): organiser = models.ForeignKey() participants = models.ManyToManyField(Profile, related_name="participants")
Now in my views.py I would like to do a query which would fetch a party for the user where there are more than 0 participants.
Something like this maybe:
user = Hipster.get(pk=1) hip_parties = Party.objects.filter(organiser=user, len(participants) > 0)
What’s the best way of doing it?
If this works this is how I would do it.
Best way can mean a lot of things: best performance, most maintainable, etc. Therefore I will not say this is the best way, but I like to stick to the ORM features as much as possible since it seems more maintainable.
from django.db.models import Count user = Hipster.objects.get(pk=1) hip_parties = (Party.objects.annotate(num_participants=Count('participants')) .filter(organiser=user, num_participants__gt=0))
Party.objects.filter(organizer=user, participants__isnull=False) Party.objects.filter(organizer=user, participants=None)
# organized by user and has more than 0 participants Party.objects.filter(organizer=user).exclude(participants=None)
Also returns distinct results