Django Framework Guide

Applies to: Django 5+, Django REST Framework, Django Channels Language: Python 3.10+

Core Principles

Batteries Included: Leverage Django's built-in features before adding third-party packages
DRY: Don't Repeat Yourself -- use abstract models, mixins, and shared utilities
Fat Models, Thin Views: Keep business logic in models and services, not views
Explicit Over Implicit: Use clear URL patterns, explicit imports, named relationships
Security by Default: CSRF, XSS protection, SQL injection prevention are built in

When to Use Django

Good fit:

Full-stack web applications with templates
Admin interface needed out of the box
Content management systems
Session-based authentication
ORM with built-in migrations

Consider alternatives:

Pure APIs with async-first needs (FastAPI)
Minimal framework overhead (Flask)
Real-time heavy workloads without Channels

Project Structure

myproject/ ├── manage.py ├── pyproject.toml ├── requirements/ │ ├── base.txt │ ├── dev.txt │ └── prod.txt ├── config/ # Project configuration │ ├── init.py │ ├── settings/ │ │ ├── init.py │ │ ├── base.py │ │ ├── dev.py │ │ └── prod.py │ ├── urls.py │ ├── wsgi.py │ └── asgi.py ├── apps/ # Django applications │ ├── users/ │ │ ├── init.py │ │ ├── admin.py │ │ ├── apps.py │ │ ├── models.py │ │ ├── views.py │ │ ├── urls.py │ │ ├── forms.py │ │ ├── serializers.py # If using DRF │ │ ├── services.py # Business logic │ │ └── tests/ │ │ ├── init.py │ │ ├── test_models.py │ │ ├── test_views.py │ │ └── test_services.py │ └── core/ # Shared utilities │ ├── init.py │ ├── models.py # Abstract base models │ └── mixins.py ├── templates/ │ ├── base.html │ └── components/ ├── static/ │ ├── css/ │ └── js/ └── tests/ └── conftest.py

Split settings into base.py , dev.py , prod.py
Group apps under apps/ directory
Keep core/ app for shared abstract models and utilities
Place business logic in services.py , not in views
Co-locate tests inside each app under tests/ directory

Guardrails

Settings

Never hardcode SECRET_KEY -- use python-decouple or environment variables
Split settings: base.py (shared), dev.py (debug), prod.py (secure)
Always define AUTH_USER_MODEL before first migration
Set DEFAULT_AUTO_FIELD = "django.db.models.BigAutoField"
Use ALLOWED_HOSTS in production (never ["*"] )

Models

Always define str on every model
Always set class Meta with db_table , ordering , and indexes
Use abstract base models for shared fields (TimeStampedModel , UUIDModel )
Use TextChoices /IntegerChoices for status fields (not raw strings)
Add related_name to all ForeignKey and OneToOneField relationships
Use on_delete explicitly: CASCADE , PROTECT , SET_NULL , SET_DEFAULT
Add database indexes for frequently queried fields
Use validators at model level for domain constraints

Abstract Base Models

apps/core/models.py

from django.db import models import uuid

class TimeStampedModel(models.Model): """Abstract base with created/updated timestamps.""" created_at = models.DateTimeField(auto_now_add=True) updated_at = models.DateTimeField(auto_now=True)

class Meta:
    abstract = True

class UUIDModel(models.Model): """Abstract base with UUID primary key.""" id = models.UUIDField( primary_key=True, default=uuid.uuid4, editable=False )

class Meta:
    abstract = True

Custom User Model

Always create a custom user model before the first migration
Extend AbstractUser (not AbstractBaseUser unless you need full control)
Set AUTH_USER_MODEL = "users.User" in settings

apps/users/models.py

from django.contrib.auth.models import AbstractUser from django.db import models from apps.core.models import TimeStampedModel, UUIDModel

class User(AbstractUser, UUIDModel, TimeStampedModel): email = models.EmailField(unique=True) USERNAME_FIELD = "email" REQUIRED_FIELDS = ["username"]

class Meta:
    db_table = "users"
    ordering = ["-created_at"]
    indexes = [models.Index(fields=["email"])]

def __str__(self) -> str:
    return self.email

Views and URLs

Class-Based Views (CBVs)

Use ListView , DetailView , CreateView , UpdateView for CRUD
Use LoginRequiredMixin for authenticated views
Override get_queryset() to add filtering and select_related /prefetch_related
Override form_valid() to inject the current user

from django.views.generic import ListView from django.db.models import Q from .models import Product

class ProductListView(ListView): model = Product template_name = "products/list.html" context_object_name = "products" paginate_by = 20

def get_queryset(self):
    qs = Product.objects.filter(
        status=Product.Status.PUBLISHED
    )
    search = self.request.GET.get("q")
    if search:
        qs = qs.filter(
            Q(name__icontains=search)
            | Q(description__icontains=search)
        )
    return qs.select_related("category")

URL Configuration

config/urls.py

from django.contrib import admin from django.urls import path, include

urlpatterns = [ path("admin/", admin.site.urls), path("api/", include("apps.api.urls")), path("", include("apps.products.urls")), ]

Use include() for app-level URL namespaces
Use app_name in each app's urls.py for reverse resolution
Serve media files in DEBUG mode only

ORM Essentials

Query Optimization

Always use select_related() for ForeignKey/OneToOne (SQL JOIN)
Always use prefetch_related() for ManyToMany/reverse FK (separate query)
Use only() or defer() to limit fields when not all columns needed
Never call Model.objects.all() without pagination or limits
Use F() expressions for database-level operations
Use Q() objects for complex lookups

Avoiding N+1 Queries

BAD: N+1 queries

for product in Product.objects.all(): print(product.category.name) # Extra query per product

GOOD: Single JOIN query

for product in Product.objects.select_related("category"): print(product.category.name) # No extra queries

Transactions

Use @transaction.atomic for multi-step writes
Use select_for_update() for optimistic locking

from django.db import transaction

@transaction.atomic def transfer_stock(source_id, dest_id, qty): source = Product.objects.select_for_update().get(id=source_id) dest = Product.objects.select_for_update().get(id=dest_id) source.stock -= qty dest.stock += qty source.save(update_fields=["stock"]) dest.save(update_fields=["stock"])

Admin Configuration

from django.contrib import admin from .models import Product

@admin.register(Product) class ProductAdmin(admin.ModelAdmin): list_display = ["name", "category", "price", "status"] list_filter = ["status", "category", "created_at"] search_fields = ["name", "description"] prepopulated_fields = {"slug": ("name",)} readonly_fields = ["created_at", "updated_at"] ordering = ["-created_at"]

fieldsets = (
    (None, {"fields": ("name", "slug", "description")}),
    ("Pricing", {"fields": ("price", "stock")}),
    ("Classification", {"fields": ("category", "status")}),
    ("Timestamps", {
        "fields": ("created_at", "updated_at"),
        "classes": ("collapse",),
    }),
)

Always register models with @admin.register(Model)
Use list_display for useful columns, list_filter for filtering
Use prepopulated_fields for slug generation
Group fields with fieldsets for organized admin forms

Django REST Framework (DRF)

Settings

REST_FRAMEWORK = { "DEFAULT_AUTHENTICATION_CLASSES": [ "rest_framework.authentication.SessionAuthentication", "rest_framework_simplejwt.authentication.JWTAuthentication", ], "DEFAULT_PERMISSION_CLASSES": [ "rest_framework.permissions.IsAuthenticated", ], "DEFAULT_PAGINATION_CLASS": ( "rest_framework.pagination.PageNumberPagination" ), "PAGE_SIZE": 20, "DEFAULT_THROTTLE_RATES": { "anon": "100/hour", "user": "1000/hour", }, }

ViewSets and Routers

Use ModelViewSet for full CRUD
Use @action(detail=True/False) for custom endpoints
Override get_serializer_class() for different read/write serializers
Override get_queryset() to add select_related /prefetch_related

from rest_framework import viewsets from rest_framework.decorators import action from rest_framework.response import Response

class ProductViewSet(viewsets.ModelViewSet): queryset = Product.objects.select_related("category") permission_classes = [IsAuthenticatedOrReadOnly]

def get_serializer_class(self):
    if self.action in ["create", "update", "partial_update"]:
        return ProductCreateSerializer
    return ProductSerializer

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

@action(detail=True, methods=["post"])
def publish(self, request, pk=None):
    product = self.get_object()
    product.status = Product.Status.PUBLISHED
    product.save(update_fields=["status"])
    return Response({"status": "published"})

Serializers

Use ModelSerializer for standard CRUD
Add read_only_fields for computed/auto fields
Validate in validate_<field>() or validate() methods
Use nested serializers for read, flat IDs for write

Security Essentials

CSRF: Enabled by default for forms; use @csrf_exempt sparingly
XSS: Django templates auto-escape by default; never use |safe with user data
SQL Injection: ORM uses parameterized queries; never use raw SQL with string formatting
Clickjacking: X-Frame-Options middleware enabled by default
HTTPS: Set SECURE_SSL_REDIRECT = True in production
HSTS: Set SECURE_HSTS_SECONDS in production
Cookies: Set SESSION_COOKIE_SECURE = True and CSRF_COOKIE_SECURE = True
Passwords: Use AUTH_PASSWORD_VALIDATORS (enabled by default)
CORS: Use django-cors-headers with explicit allowed origins (never CORS_ALLOW_ALL_ORIGINS in production)

Testing

Standards

Use pytest with pytest-django (not Django's built-in test runner)
Mark database tests with @pytest.mark.django_db
Use factory-boy or fixtures for test data
Use APIClient for DRF endpoint testing
Coverage target: >80% for business logic
Test file naming: test_models.py , test_views.py , test_services.py

Fixtures

conftest.py

import pytest from rest_framework.test import APIClient from apps.users.models import User

@pytest.fixture def api_client(): return APIClient()

@pytest.fixture def user(db): return User.objects.create_user( username="testuser", email="test@example.com", password="testpass123", )

@pytest.fixture def authenticated_client(api_client, user): api_client.force_authenticate(user=user) return api_client

Commands Reference

Development

python manage.py runserver python manage.py shell_plus # django-extensions

Migrations

python manage.py makemigrations python manage.py migrate python manage.py showmigrations

Testing

pytest pytest -v --cov=apps --cov-report=html pytest apps/products/ -k "test_create"

Database

python manage.py dbshell python manage.py dumpdata products > fixtures/products.json python manage.py loaddata fixtures/products.json

Static files

python manage.py collectstatic

Celery

celery -A config worker -l info celery -A config beat -l info

Dependencies

Base: Django>=5.0 , djangorestframework , django-cors-headers , django-filter , djangorestframework-simplejwt , python-decouple , psycopg2-binary , whitenoise

Dev: pytest , pytest-django , pytest-cov , factory-boy , django-debug-toolbar , django-extensions , black , ruff , mypy , django-stubs

Best Practices

Use select_related and prefetch_related for every queryset
Create indexes for frequently queried fields
Use @transaction.atomic for multi-step operations
Validate at both model level and serializer level
Write services for business logic (not in views)
Use signals sparingly (prefer explicit service calls)
Cache expensive queries with Django cache framework
Use environment variables for all configuration

Don't

Put business logic in views
Use raw SQL without parameterization
Ignore N+1 query problems
Store sensitive data in settings files
Use Model.objects.all() without limits
Skip migrations in production
Use CORS_ALLOW_ALL_ORIGINS = True in production
Use |safe template filter with user-provided data

Advanced Topics

For detailed code examples and advanced patterns, see:

references/patterns.md -- DRF serializers, middleware, services, signals, Celery tasks, management commands, deployment, and testing patterns

External References

Django Documentation
Django REST Framework
Two Scoops of Django
Django Best Practices

django

Safety Notice

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apps/core/models.py

apps/users/models.py

config/urls.py

BAD: N+1 queries

GOOD: Single JOIN query

conftest.py

Development

Migrations

Testing

Database

Static files

Celery

Source Transparency

Related Skills

actix-web

frontend-design

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