Remove results with field==0 from serializer response - django

Question

I use ModelSerializer to return serialized data of a model:
class CategorySerializer(serializers.ModelSerializer):
category_count = serializers.SerializerMethodField('_category_count')
def _category_count(self, obj):
category_obj = Category.objects.get(id=obj.id)
questions_count = Question.objects.filter(category=category_obj).count()
return questions_count
class Meta:
model = Category
fields = ["id", "category", "category_count"]
What I get write now is here:
[{
"category": "orzecznictwo lekarskie",
"category_count": 0,
"id": 9
},
{
"category": "zdrowie publiczne",
"category_count": 1,
"id": 10
}
]
I want to remove objects with category_count == 0 from serialization
[
{
"category": "zdrowie publiczne",
"category_count": 1,
"id": 10
}
]
Thank you for your help.
EDIT:
class Question(models.Model):
category = models.ForeignKey(Category, on_delete=models.CASCADE)
question = models.TextField(blank=True, null=True)
(...)
class Category(models.Model):
category = models.TextField()
category_slug = models.CharField(max_length=50)

Answer 1

You're generating the field inside the serializer and then want to discard the object. That's not how things work: serializers merely change representation of data. Which data is displayed is determined in views.
class CategoryListView(generics.ListAPIView):
def get_queryset(self):
return models.Category.objects.annotate(
question_count=Count("question_set")
).exclude(question_count=0)
And in the serializer, you don't have to create the count any more and add the 'question_count' to Meta.fields.
Recommended reading.
Edit:
Forgot that DRF will check the field on the model and fail, so you need to declare the field:
class CategoryWithQuestionCount(serializers.ModelSerializer):
question_count = serializers.IntegerField(read_only=True)
class Meta:
model = models.Category
fields = ("pk", "category", "question_count")

Answer 2

I'm not sure about removing it in the ModelSerializer. But you can try overriding get_queryset() or changing the queryset in your View:
queryset = Class.objects.exclude(dzial_liczba_pytan=0)