Django serializers vs DRF serializers

“Serializer” means two different things in a Django codebase, and mixing them up is a common interview stumble. Django’s own serializers (django.core.serializers) dump and load model instances for fixtures and data migration. DRF serializers validate API input and render API output. They share a name and nothing else.

Django’s own serializers: fixtures, not APIs

from django.core import serializers

data = serializers.serialize("json", Order.objects.filter(status="paid"))
for obj in serializers.deserialize("json", data):
    obj.save()                      # bypasses model validation and save() logic

python manage.py dumpdata shop.Order --indent 2 > orders.json
python manage.py loaddata orders.json

The output is model-shaped ({"model": "shop.order", "pk": 7, "fields": {...}}), includes every field, and loading it calls save_base directly: no full_clean(), no custom save(), and signals receive raw=True. That is right for fixtures and test data, and wrong for an API, where you need validation, a public shape that is not your schema, and control over which fields leave the server.

Natural keys

Fixtures that refer to rows by primary key break when loaded into a database whose ids differ. Natural keys refer to rows by a unique business value instead:

class CountryManager(models.Manager):
    def get_by_natural_key(self, code):
        return self.get(code=code)

class Country(models.Model):
    code = models.CharField(max_length=2, unique=True)
    objects = CountryManager()

    def natural_key(self):
        return (self.code,)

dumpdata --natural-foreign --natural-primary then writes "country": ["DE"] instead of "country": 3.

DRF serializers and viewset actions

For APIs, DRF serializers do validation and conversion in both directions, and viewset actions map HTTP methods and extra endpoints onto them. They are covered in the DRF notes:

• DRF Serializers - Serializer, ModelSerializer, fields, SerializerMethodField
• DRF Validation - field, object and model-level validation
• DRF Routers and Custom Actions - routers, standard actions, @action for extra endpoints
• DRF Nested Writable Serializers - nested writes
• DRF Performance and the N+1 Problem - serializer cost and N+1

Related

• Django vs Django REST Framework - what DRF adds to Django
• Django Migrations: A Comprehensive Guide - data migrations, where fixtures sometimes appear
• Django signals - the raw=True flag during fixture loading