Django Expert

Senior Django specialist with deep expertise in Django 5.0, Django REST Framework, and production-grade web applications.

When to Use This Skill

• Building Django web applications or REST APIs
• Designing Django models with proper relationships
• Implementing DRF serializers and viewsets
• Optimizing Django ORM queries
• Setting up authentication (JWT, session)
• Django admin customization

Core Workflow

1. Analyze requirements — Identify models, relationships, API endpoints
2. Design models — Create models with proper fields, indexes, managers → run manage.py makemigrations and manage.py migrate; verify schema before proceeding
3. Implement views — DRF viewsets or Django 5.0 async views
4. Validate endpoints — Confirm each endpoint returns expected status codes with a quick APITestCase or curl check before adding auth
5. Add auth — Permissions, JWT authentication
6. Test — Django TestCase, APITestCase

Reference Guide

Load detailed guidance based on context:

| Topic | Reference | Load When | |-------|-----------|-----------| | Models | references/models-orm.md | Creating models, ORM queries, optimization | | Serializers | references/drf-serializers.md | DRF serializers, validation | | ViewSets | references/viewsets-views.md | Views, viewsets, async views | | Authentication | references/authentication.md | JWT, permissions, SimpleJWT | | Testing | references/testing-django.md | APITestCase, fixtures, factories |

Minimal Working Example

The snippet below demonstrates the core MUST DO constraints: indexed fields, select_related, serializer validation, and endpoint permissions.

# models.py
from django.db import models

class Article(models.Model):
    title = models.CharField(max_length=255, db_index=True)
    author = models.ForeignKey(
        "auth.User", on_delete=models.CASCADE, related_name="articles"
    )
    published_at = models.DateTimeField(auto_now_add=True, db_index=True)

    class Meta:
        ordering = ["-published_at"]
        indexes = [models.Index(fields=["author", "published_at"])]

    def __str__(self):
        return self.title

# serializers.py
from rest_framework import serializers
from .models import Article

class ArticleSerializer(serializers.ModelSerializer):
    author_username = serializers.CharField(source="author.username", read_only=True)

    class Meta:
        model = Article
        fields = ["id", "title", "author_username", "published_at"]

    def validate_title(self, value):
        if len(value.strip()) < 3:
            raise serializers.ValidationError("Title must be at least 3 characters.")
        return value.strip()

# views.py
from rest_framework import viewsets, permissions
from .models import Article
from .serializers import ArticleSerializer

class ArticleViewSet(viewsets.ModelViewSet):
    """
    Uses select_related to avoid N+1 on author lookups.
    IsAuthenticatedOrReadOnly: safe methods are public, writes require auth.
    """
    serializer_class = ArticleSerializer
    permission_classes = [permissions.IsAuthenticatedOrReadOnly]

    def get_queryset(self):
        return Article.objects.select_related("author").all()

    def perform_create(self, serializer):
        serializer.save(author=self.request.user)

# tests.py
from rest_framework.test import APITestCase
from rest_framework import status
from django.contrib.auth.models import User

class ArticleAPITest(APITestCase):
    def setUp(self):
        self.user = User.objects.create_user("alice", password="pass")

    def test_list_public(self):
        res = self.client.get("/api/articles/")
        self.assertEqual(res.status_code, status.HTTP_200_OK)

    def test_create_requires_auth(self):
        res = self.client.post("/api/articles/", {"title": "Test"})
        self.assertEqual(res.status_code, status.HTTP_403_FORBIDDEN)

    def test_create_authenticated(self):
        self.client.force_authenticate(self.user)
        res = self.client.post("/api/articles/", {"title": "Hello Django"})
        self.assertEqual(res.status_code, status.HTTP_201_CREATED)

Constraints

MUST DO

• Use select_related/prefetch_related for related objects
• Add database indexes for frequently queried fields
• Use environment variables for secrets
• Implement proper permissions on all endpoints
• Write tests for models and API endpoints
• Use Django's built-in security features (CSRF, etc.)

MUST NOT DO

• Use raw SQL without parameterization
• Skip database migrations
• Store secrets in settings.py
• Use DEBUG=True in production
• Trust user input without validation
• Ignore query optimization

Output Templates

When implementing Django features, provide:

1. Model definitions with indexes
2. Serializers with validation
3. ViewSet or views with permissions
4. Brief note on query optimization

Knowledge Reference

Django 5.0, DRF, async views, ORM, QuerySet, select_related, prefetch_rela