Django Development

Django Development Guide

This skill provides comprehensive guidance for building robust Django web applications following Django 5.2 standards and industry-proven best practices.

When to Use This Skill

Use this skill when:

• Starting a new Django project or app
• Implementing models, views, templates, or forms
• Configuring Django settings or URL routing
• Addressing security concerns in Django applications
• Writing tests or deploying Django applications
• Following Django conventions and best practices
• Troubleshooting Django-specific issues

Core Principles

Convention Over Configuration: Django follows established conventions that reduce boilerplate and decision fatigue. Follow Django patterns rather than reinventing solutions.

DRY (Don't Repeat Yourself): Extract reusable code into models, managers, mixins, template tags, and middleware.

Security by Default: Django provides built-in protection against common vulnerabilities. Never disable security features without understanding the implications.

Explicit is Better Than Implicit: Code should be clear and self-documenting. Use descriptive names and follow Django naming conventions.

Development Workflow

Phase 1: Project Planning and Setup

1.1 Understand Requirements

Before creating a Django project, clarify:

• Data models: What entities exist and how do they relate?
• User interactions: What actions can users perform?
• Authentication needs: Who can access what?
• Third-party integrations: External APIs or services needed?

1.2 Initialize Project Structure

Create a new Django project:

# Create project directory
mkdir myproject
cd myproject

# Create virtual environment
python -m venv venv
source venv/bin/activate  # On Windows: venv\Scripts\activate

# Install Django
pip install django

# Start project
django-admin startproject config .

Key distinction: A project contains configuration and settings, while apps contain specific functionality.

1.3 Configure Initial Settings

Load the detailed configuration guide: ⚙️ Settings Configuration Reference

Essential initial settings:

• SECRET_KEY: Must be 50+ characters, use environment variables, never commit to version control
• DEBUG: Set to False in production
• ALLOWED_HOSTS: Configure for your domain
• DATABASES: Configure database connection
• INSTALLED_APPS: Register Django apps and third-party packages
• MIDDLEWARE: Ensure SecurityMiddleware is enabled and properly ordered

Phase 2: Data Modeling

2.1 Design Your Models

Models are the single source of truth for your data. Before coding:

• Identify entities (User, Post, Comment, etc.)
• Define relationships (one-to-many, many-to-many, one-to-one)
• Determine required fields and constraints
• Plan for data validation and business logic

2.2 Implement Models

Load the comprehensive models guide: 📊 Models and Database Reference

Model implementation checklist:

• Use appropriate field types (CharField, IntegerField, ForeignKey, etc.)
• Set field options (null, blank, default, unique)
• Define relationships with proper related_name
• Implement __str__() method for readable representation
• Add get_absolute_url() for object URLs
• Configure Meta class (ordering, verbose_name, constraints)
• Create custom managers for reusable queries
• Override save() or delete() for custom behavior (call super())

2.3 Create and Apply Migrations

After defining or modifying models:

# Create migration files
python manage.py makemigrations

# Review generated migrations
python manage.py sqlmigrate appname 0001

# Apply migrations
python manage.py migrate

Migration best practices:

• Review migrations before applying
• Use descriptive migration names with --name
• Never edit applied migrations
• Handle data migrations separately
• Test migrations on development data first

Phase 3: Views and URL Routing

3.1 Plan Your Views

Views handle request processing and response generation. Determine:

• Which views are needed (list, detail, create, update, delete)
• Function-based views (FBVs) vs class-based views (CBVs)
• Authentication and permission requirements
• Template rendering vs API responses

3.2 Implement Views

Load the comprehensive views guide: 🎯 Views and URL Routing Reference

View patterns:

Function-Based Views (FBVs):

• Simple, explicit, good for unique logic
• Full control over request handling
• Use for complex or non-standard workflows

Class-Based Views (CBVs):

• Reusable, extensible, built-in functionality
• Generic views for common patterns (ListView, DetailView, CreateView)
• Use for standard CRUD operations

3.3 Configure URL Routing

URL configuration best practices:

• Use descriptive URL patterns with meaningful names
• Organize URLs by app using include()
• Use path converters (<int:pk>, <slug:slug>)
• Name all URL patterns for reverse() and {% url %}
• Keep URLs RESTful and intuitive

Phase 4: Templates and Forms

4.1 Create Templates

Load the templates and forms guide: 🎨 Templates and Forms Reference

Template best practices:

• Use template inheritance (base template + child templates)
• Leverage template tags and filters
• Keep logic minimal (belongs in views/models)
• Use {% static %} for static files
• Take advantage of automatic XSS protection

4.2 Build Forms

Form implementation checklist:

• Use ModelForm when tied to models
• Use Form for non-model forms
• Implement custom validation with clean_<field>() methods
• Add form-level validation with clean()
• Use widgets to customize form rendering
• Handle file uploads with proper validation
• Include CSRF token in templates ({% csrf_token %})

Phase 5: Security Implementation

Security must be considered throughout development, not as an afterthought.

Load the comprehensive security guide: 🔒 Security Best Practices Reference

Security checklist:

• Keep SECRET_KEY secure and environment-specific
• Set DEBUG = False in production
• Configure ALLOWED_HOSTS appropriately
• Enable HTTPS and secure cookies
• Use CSRF protection (enabled by default)
• Leverage built-in XSS protection
• Use QuerySet parameterization (avoid raw SQL)
• Validate and sanitize user input
• Implement proper authentication and authorization
• Limit file upload sizes and types
• Set appropriate Content Security Policy headers
• Enable clickjacking protection

Phase 6: Testing

Load the testing guide: ✅ Testing and Quality Assurance Reference

Testing best practices:

• Write tests alongside code development
• Test models, views, forms, and custom logic
• Use TestCase for database-touching tests
• Use SimpleTestCase for non-database tests
• Mock external services and APIs
• Aim for high coverage of critical paths
• Use Django's test client for view testing
• Test authentication and permissions

Run tests:

# Run all tests
python manage.py test

# Run specific app tests
python manage.py test myapp

# Run with coverage
coverage run --source='.' manage.py test
coverage report

Phase 7: Deployment Preparation

Before deploying to production:

Load the deployment guide: 🚀 Testing and Deployment Reference

Deployment checklist:

• Run python manage.py check --deploy
• Set DEBUG = False
• Configure production database
• Set up static file serving (use collectstatic)
• Configure media file storage
• Set secure cookies and HTTPS settings
• Configure logging
• Set up error monitoring (Sentry, etc.)
• Configure caching strategy
• Review and optimize database queries
• Set up backup procedures
• Document deployment process

Reference Documentation

Load these comprehensive guides as needed during development:

Core References

• ⚙️ Settings Configuration - Complete settings guide including database configuration, static files, middleware, internationalization, and environment-specific settings

• 📊 Models and Database - Comprehensive model development guide covering field types, relationships, Meta options, custom managers, model methods, inheritance patterns, and migrations

• 🎯 Views and URL Routing - Complete guide to function-based and class-based views, generic views, URL configuration, request/response handling, and middleware

• 🎨 Templates and Forms - Template inheritance, template tags/filters, context processors, form creation, validation, widgets, and formsets

• 🔒 Security Best Practices - Comprehensive security guide covering CSRF, XSS, SQL injection, clickjacking, authentication, HTTPS configuration, and common vulnerabilities

• ✅ Testing and Deployment - Testing strategies, test types, coverage, deployment preparation, production configuration, and monitoring

Common Patterns and Quick Reference

Creating a New App

python manage.py startapp myapp

Then add to INSTALLED_APPS in settings.

Basic Model Pattern

from django.db import models

class MyModel(models.Model):
    name = models.CharField(max_length=200)
    created_at = models.DateTimeField(auto_now_add=True)

    class Meta:
        ordering = ['-created_at']
        verbose_name_plural = "My Models"

    def __str__(self):
        return self.name

    def get_absolute_url(self):
        from django.urls import reverse
        return reverse('mymodel-detail', args=[str(self.id)])

Basic View Pattern

from django.views.generic import ListView, DetailView
from .models import MyModel

class MyModelListView(ListView):
    model = MyModel
    template_name = 'myapp/mymodel_list.html'
    context_object_name = 'items'
    paginate_by = 20

class MyModelDetailView(DetailView):
    model = MyModel
    template_name = 'myapp/mymodel_detail.html'

Basic URL Pattern

from django.urls import path
from . import views

app_name = 'myapp'

urlpatterns = [
    path('', views.MyModelListView.as_view(), name='list'),
    path('<int:pk>/', views.MyModelDetailView.as_view(), name='detail'),
]

Basic Template Pattern

{% extends "base.html" %}
{% load static %}

{% block title %}{{ object.name }}{% endblock %}

{% block content %}
<h1>{{ object.name }}</h1>
<p>Created: {{ object.created_at|date:"F d, Y" }}</p>
{% endblock %}

Progressive Workflow

Django development is iterative. For new features:

1. Design the data model → Create/update models → Make migrations
2. Create views → Implement business logic → Handle requests
3. Configure URLs → Map URLs to views → Name patterns
4. Build templates → Create HTML with Django template language
5. Add forms → Handle user input → Validate data
6. Write tests → Test models, views, forms → Ensure quality
7. Review security → Check for vulnerabilities → Follow best practices

Remember: Django documentation at https://docs.djangoproject.com/en/5.2/ is comprehensive and should be consulted for detailed API references and advanced topics.

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