rides.py

from rider.models import *

rides_with_ck_ids = CheckRide.objects.all().values_list('ride_id', flat=True)
rides_ids = Ride.objects.all().values_list('id', flat=True)

rides_without_ck_ids = []
for id in rides_ids:
    if id not in rides_with_ck_ids:
        rides_without_ck_ids.append(id)

print(rides_without_ck_ids)

rides = Ride.objects.filter(ckride__isnull=True).count()
print([ride.id for ride in rides])