# Django Quick Reference
*Models, views, templates, ORM, forms, admin, auth*
> Source: Django Documentation (docs.djangoproject.com) ยท MIT
## Project Setup
### Create Project & App
```
pip install django
django-admin startproject mysite
cd mysite
python manage.py startapp blog
```
### Common Commands
| Command | Description |
|---------|-------------|
| `runserver` | Start dev server on port 8000 |
| `makemigrations` | Generate migration files from model changes |
| `migrate` | Apply migrations to database |
| `createsuperuser` | Create admin superuser |
| `shell` | Interactive Python shell with Django |
| `test` | Run test suite |
### Project Structure
| Command | Description |
|---------|-------------|
| `manage.py` | CLI entry point |
| `settings.py` | Project configuration |
| `urls.py` | Root URL configuration |
| `wsgi.py / asgi.py` | Server entry points |
| `apps/models.py` | Database models |
| `apps/views.py` | Request handlers |
## Models
### Define a Model
```
from django.db import models
class Post(models.Model):
title = models.CharField(max_length=200)
body = models.TextField()
created = models.DateTimeField(auto_now_add=True)
published = models.BooleanField(default=False)
```
### Field Types
| Command | Description |
|---------|-------------|
| `CharField(max_length=N)` | Short text (required max_length) |
| `TextField()` | Long text (no limit) |
| `IntegerField()` | Integer value |
| `FloatField()` | Floating point number |
| `BooleanField()` | True / False |
| `DateTimeField()` | Date and time |
| `EmailField()` | Email with validation |
| `FileField(upload_to='')` | File upload |
### Relationships
```
author = models.ForeignKey(
User, on_delete=models.CASCADE
)
tags = models.ManyToManyField(Tag, blank=True)
profile = models.OneToOneField(User, on_delete=models.CASCADE)
```
### Meta & Methods
```
class Meta:
ordering = ['-created']
verbose_name_plural = 'posts'
def __str__(self):
return self.title
```
## Views
### Function-Based View
```
from django.shortcuts import render, get_object_or_404
def post_list(request):
posts = Post.objects.filter(published=True)
return render(request, 'blog/list.html', {'posts': posts})
```
### Class-Based Views
```
from django.views.generic import ListView, DetailView
class PostListView(ListView):
model = Post
template_name = 'blog/list.html'
context_object_name = 'posts'
paginate_by = 10
```
### Common CBVs
| Command | Description |
|---------|-------------|
| `ListView` | Display list of objects |
| `DetailView` | Display single object |
| `CreateView` | Form to create object |
| `UpdateView` | Form to edit object |
| `DeleteView` | Confirm and delete object |
| `TemplateView` | Render a template (no model) |
### JSON Response
```
from django.http import JsonResponse
def api_posts(request):
data = list(Post.objects.values('id', 'title'))
return JsonResponse(data, safe=False)
```
## Templates
### Template Syntax
```
{{ variable }}
{{ post.title|truncatewords:30 }}
{% if user.is_authenticated %}
Welcome, {{ user.username }}!
{% endif %}
```
### Loops & Conditions
```
{% for post in posts %}
{{ post.title }}
{% if forloop.last %}
{% endif %}
{% empty %}
No posts yet.
{% endfor %}
```
### Template Inheritance
```
{# base.html #}
{% block content %}{% endblock %}
{# child.html #}
{% extends "base.html" %}
{% block content %}Hello
{% endblock %}
```
### Common Filters
| Command | Description |
|---------|-------------|
| `\|date:"Y-m-d"` | Format date |
| `\|default:"N/A"` | Fallback for empty values |
| `\|length` | Count items in list |
| `\|truncatewords:N` | Limit to N words |
| `\|safe` | Mark as safe HTML (no escaping) |
| `\|slugify` | URL-safe lowercase string |
## URLs
### URL Patterns
```
from django.urls import path, include
urlpatterns = [
path('', views.index, name='index'),
path('post//', views.detail, name='detail'),
path('blog/', include('blog.urls')),
]
```
### Path Converters
| Command | Description |
|---------|-------------|
| `` | Integer (e.g., 42) |
| `` | String without slashes |
| `` | Slug (letters, numbers, hyphens) |
| `` | UUID format |
| `` | Full path including slashes |
### Reverse URLs
```
from django.urls import reverse
url = reverse('detail', kwargs={'pk': 1})
# In templates: {% url 'detail' pk=post.pk %}
```
## Forms
### Model Form
```
from django import forms
class PostForm(forms.ModelForm):
class Meta:
model = Post
fields = ['title', 'body', 'published']
```
### Process Form in View
```
def create_post(request):
form = PostForm(request.POST or None)
if form.is_valid():
post = form.save(commit=False)
post.author = request.user
post.save()
return redirect('detail', pk=post.pk)
return render(request, 'blog/form.html', {'form': form})
```
### Form in Template
```
```
### Validation
```
def clean_title(self):
title = self.cleaned_data['title']
if len(title) < 5:
raise forms.ValidationError("Title too short.")
return title
```
## Admin
### Register Model
```
from django.contrib import admin
from .models import Post
@admin.register(Post)
class PostAdmin(admin.ModelAdmin):
list_display = ['title', 'author', 'created', 'published']
list_filter = ['published', 'created']
search_fields = ['title', 'body']
```
### Admin Options
| Command | Description |
|---------|-------------|
| `list_display` | Columns in list view |
| `list_filter` | Sidebar filter options |
| `search_fields` | Searchable fields |
| `prepopulated_fields` | Auto-fill (e.g., slug from title) |
| `readonly_fields` | Non-editable in admin |
| `ordering` | Default sort order |
## ORM Queries
### Basic Queries
```
Post.objects.all() # all records
Post.objects.get(pk=1) # single (raises if missing)
Post.objects.filter(published=True) # queryset
Post.objects.exclude(draft=True) # exclude matches
Post.objects.count() # total count
```
### Field Lookups
| Command | Description |
|---------|-------------|
| `field__exact` | Exact match (default) |
| `field__icontains` | Case-insensitive contains |
| `field__gt / __lt` | Greater / less than |
| `field__gte / __lte` | Greater/less than or equal |
| `field__in=[1,2,3]` | Value in list |
| `field__isnull=True` | Is NULL |
| `field__startswith` | Starts with string |
| `field__range=(a,b)` | Between a and b inclusive |
### Chaining & Aggregation
```
from django.db.models import Q, Count, Avg
Post.objects.filter(
Q(title__icontains='django') | Q(body__icontains='django')
).order_by('-created')[:10]
Post.objects.aggregate(avg_views=Avg('views'))
```
### Create, Update, Delete
```
post = Post.objects.create(title='New', body='...')
post.title = 'Updated'
post.save()
Post.objects.filter(draft=True).update(published=False)
post.delete()
```
## Authentication
### Login / Logout
```
from django.contrib.auth import authenticate, login, logout
user = authenticate(request, username='admin', password='pw')
if user is not None:
login(request, user)
```
### Protect Views
```
from django.contrib.auth.decorators import login_required
@login_required
def dashboard(request):
return render(request, 'dashboard.html')
```
### Auth URLs
```
# urls.py
path('accounts/', include('django.contrib.auth.urls'))
# Provides: login, logout, password_change, password_reset
```
### Template Auth
```
{% if user.is_authenticated %}
Hi, {{ user.username }}
Logout
{% else %}
Login
{% endif %}
```
## Settings
### Key Settings
| Command | Description |
|---------|-------------|
| `DEBUG` | `True` for dev, `False` for production |
| `ALLOWED_HOSTS` | List of valid hostnames |
| `SECRET_KEY` | Cryptographic signing key (keep secret) |
| `DATABASES` | DB engine, name, host, credentials |
| `INSTALLED_APPS` | Registered apps list |
| `STATIC_URL` | URL prefix for static files |
| `MEDIA_URL / MEDIA_ROOT` | User-uploaded file paths |
### Database Config
```
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.postgresql',
'NAME': 'mydb',
'USER': 'dbuser',
'HOST': 'localhost',
'PORT': '5432',
}
}
```
### Static Files
```
STATIC_URL = '/static/'
STATICFILES_DIRS = [BASE_DIR / 'static']
# In templates: {% load static %}
#
```