How to add extra fields in ValueQuerySet (Django)? - json

Question

Basically, I want to convert the query_set to JSON. But I also want to add one more field something like size = some number in the query_set which is not present in the query_set attributes (it is computed attribute). Can you tell me how to do it?
query_set = PotholeCluster.objects.all().values('bearing', 'center_lat', 'center_lon', 'grid_id')
return JsonResponse(list(query_set), safe=False)
I tried the code below. It works, but I would like to know if there is any cleaner way to do this.
query_set = PotholeCluster.objects.all()
response_list = []
for pc in query_set:
d = {}
d['bearing'] = pc.get_bearing()
d['center_lat'] = pc.center_lat
d['center_lon'] = pc.center_lat
d['grid_id'] = pc.grid_id
d['size'] = pc.pothole_set.all().count()
response_list.append(d)
serialized = json.dumps(response_list)
return HttpResponse(serialized, content_type='application/json')
class PotholeCluster(models.Model):
center_lat = models.FloatField(default=0)
center_lon = models.FloatField(default=0)
snapped_lat = models.FloatField(default=0)
snapped_lon = models.FloatField(default=0)
size = models.IntegerField(default=-1)
# avgspeed in kmph
speed = models.FloatField(default=-1)
# in meters
accuracy = models.FloatField(default=-1)
# avg bearing in degree
bearing = models.FloatField(default=-1)
grid = models.ForeignKey(
Grid,
on_delete=models.SET_NULL,
null=True,
blank=True
)
def __str__(self):
raw_data = serialize('python', [self])
output = json.dumps(raw_data[0]['fields'])
return "pk = {}|{}".format(self.id, output)
def get_bearing(self):
if self.bearing != -1:
return self.bearing
potholes = self.pothole_set.all()
bearings = [pothole.location.bearing for pothole in potholes]
bearings.sort()
i = 0
if bearings[-1] >= 350:
while bearings[-1] - bearings[i] >= 340:
if bearings[i] <= 10:
bearings[i] += 360
i += 1
self.bearing = sum(bearings) / len(bearings) % 360
self.save()
return self.bearing
def get_size(self):
if self.size != -1:
return self.size
self.size = len(self.pothole_set.all())
self.save()
return self.size