🦄 Python 09 — Django Framework

1. Django ဆိုတာ

Django က Python မှာ အသုံးအများဆုံး full-stack web framework ပါ။ "Batteries included" philosophy — ORM, admin panel, auth, forms, templating, CSRF protection, migrations တွေ built-in ပါတယ်။

2. Setup & New Project

# virtual environment အရင်ဆောက်
python -m venv venv
source venv/bin/activate       # Mac/Linux
venv\Scripts\activate           # Windows

# Django install
pip install django

# New project create
django-admin startproject mysite .
# (dot ထည့်ရင် current dir ထဲ, မထည့်ရင် subfolder ဆောက်)

# Development server start
python manage.py runserver
# http://127.0.0.1:8000 မှာ "The install worked!" မြင်ရမယ်

Project Structure

mysite/
├── manage.py           ← CLI entry point (runserver, migrate, etc.)
├── mysite/
│   ├── settings.py     ← all configuration
│   ├── urls.py         ← URL routing (main)
│   ├── wsgi.py         ← production server entry
│   └── asgi.py         ← async server entry
└── db.sqlite3          ← default SQLite database (auto-created)

3. App တည်ဆောက်ခြင်း

Django project = multiple apps. App တစ်ခုက feature set တစ်ခု (blog, shop, users).

# New app create
python manage.py startapp blog

# settings.py မှာ register လုပ်ရမယ်
INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    ...
    'blog',   # ← ထည့်ပါ
]

App Structure

blog/
├── models.py       ← database models (ORM)
├── views.py        ← request handlers
├── urls.py         ← URL patterns (app-level)
├── admin.py        ← admin registration
├── forms.py        ← form classes
├── templates/      ← HTML templates
│   └── blog/
│       ├── list.html
│       └── detail.html
└── migrations/     ← database migration files

4. Models & Database ORM

# blog/models.py
from django.db import models
from django.contrib.auth.models import User

class Post(models.Model):
    title   = models.CharField(max_length=200)
    content = models.TextField()
    author  = models.ForeignKey(User, on_delete=models.CASCADE)
    created = models.DateTimeField(auto_now_add=True)
    updated = models.DateTimeField(auto_now=True)
    published = models.BooleanField(default=False)

    class Meta:
        ordering = ['-created']   # newest first

    def __str__(self):
        return self.title

# migrations run
python manage.py makemigrations blog   # migration file ဆောက်
python manage.py migrate               # database ကို apply

# Django Shell မှာ data test
python manage.py shell
>>> from blog.models import Post
>>> Post.objects.create(title="First Post", content="Hello!", author_id=1, published=True)
>>> Post.objects.all()
>>> Post.objects.filter(published=True)
>>> Post.objects.filter(title__contains="First")  # field lookups
>>> Post.objects.get(id=1)
>>> Post.objects.order_by('-created')[:5]          # top 5 newest

Relationships

# One-to-Many (ForeignKey)
author = models.ForeignKey(User, on_delete=models.CASCADE)

# Many-to-Many
tags = models.ManyToManyField('Tag', blank=True)

# One-to-One
profile = models.OneToOneField(User, on_delete=models.CASCADE)

# Cascade options
on_delete=models.CASCADE       # parent delete → child delete
on_delete=models.SET_NULL      # parent delete → child.fk = NULL
on_delete=models.PROTECT       # prevent parent delete if children exist

5. Views & URLs

Function-based Views (FBV)

# blog/views.py
from django.shortcuts import render, get_object_or_404, redirect
from .models import Post

def post_list(request):
    posts = Post.objects.filter(published=True)
    return render(request, 'blog/list.html', {'posts': posts})

def post_detail(request, pk):
    post = get_object_or_404(Post, pk=pk)
    return render(request, 'blog/detail.html', {'post': post})

def post_create(request):
    if request.method == 'POST':
        title   = request.POST.get('title')
        content = request.POST.get('content')
        Post.objects.create(title=title, content=content,
                            author=request.user, published=True)
        return redirect('post_list')
    return render(request, 'blog/form.html')

URL Patterns

# blog/urls.py
from django.urls import path
from . import views

urlpatterns = [
    path('',        views.post_list,   name='post_list'),
    path('<int:pk>/', views.post_detail, name='post_detail'),
    path('new/',    views.post_create,  name='post_create'),
]

# mysite/urls.py (main)
from django.contrib import admin
from django.urls import path, include

urlpatterns = [
    path('admin/', admin.site.urls),
    path('blog/',  include('blog.urls')),
    path('',       include('blog.urls')),
]

6. Templates (Django Template Language)

{# blog/templates/blog/list.html #}
<!DOCTYPE html>
<html>
<head><title>Blog</title></head>
<body>
  <h1>Blog Posts</h1>
  {% for post in posts %}
    <div>
      <h2><a href="{% url 'post_detail' post.pk %}">{{ post.title }}</a></h2>
      <p>{{ post.created|date:"Y-m-d" }}</p>
      <p>{{ post.content|truncatewords:30 }}</p>
    </div>
  {% empty %}
    <p>No posts yet.</p>
  {% endfor %}
</body>
</html>

Template Inheritance

{# templates/base.html #}
<!DOCTYPE html>
<html>
<head>
  <title>{% block title %}My Site{% endblock %}</title>
</head>
<body>
  <nav><a href="/">Home</a></nav>
  {% block content %}{% endblock %}
</body>
</html>

{# blog/list.html extends base #}
{% extends "base.html" %}
{% block title %}Blog{% endblock %}
{% block content %}
  {% for post in posts %}...{% endfor %}
{% endblock %}

7. Forms & Validation

# blog/forms.py
from django import forms
from .models import Post

class PostForm(forms.ModelForm):
    class Meta:
        model  = Post
        fields = ['title', 'content', 'published']
        widgets = {
            'content': forms.Textarea(attrs={'rows': 8}),
        }

# blog/views.py
def post_create(request):
    form = PostForm(request.POST or None)
    if form.is_valid():
        post = form.save(commit=False)
        post.author = request.user
        post.save()
        return redirect('post_list')
    return render(request, 'blog/form.html', {'form': form})

{# form.html template #}
<form method="post">
  {% csrf_token %}
  {{ form.as_p }}
  <button type="submit">Save</button>
</form>

8. Admin Panel

# blog/admin.py
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', 'content']
    list_editable = ['published']   # edit published directly in list

# Superuser ဆောက်
python manage.py createsuperuser

# http://127.0.0.1:8000/admin/ မှာ login ဝင်ပြီး data manage လုပ်နိုင်

9. REST API (Django REST Framework)

pip install djangorestframework

# settings.py
INSTALLED_APPS += ['rest_framework']

# blog/serializers.py
from rest_framework import serializers
from .models import Post

class PostSerializer(serializers.ModelSerializer):
    class Meta:
        model  = Post
        fields = ['id', 'title', 'content', 'created', 'published']

# blog/views.py
from rest_framework import viewsets
from .models import Post
from .serializers import PostSerializer

class PostViewSet(viewsets.ModelViewSet):
    queryset = Post.objects.filter(published=True)
    serializer_class = PostSerializer

# blog/urls.py
from rest_framework.routers import DefaultRouter
from .views import PostViewSet

router = DefaultRouter()
router.register('posts', PostViewSet)

urlpatterns = router.urls
# GET  /api/posts/       → list
# POST /api/posts/       → create
# GET  /api/posts/1/     → detail
# PUT  /api/posts/1/     → update
# DELETE /api/posts/1/  → delete

10. Static Files & Settings

# settings.py key settings
DEBUG = True   # production မှာ False ထားမယ်

ALLOWED_HOSTS = ['localhost', '127.0.0.1']

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': BASE_DIR / 'db.sqlite3',
    }
}

# PostgreSQL switch
DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql',
        'NAME': 'mydb',
        'USER': 'postgres',
        'PASSWORD': 'password',
        'HOST': 'localhost',
        'PORT': '5432',
    }
}

STATIC_URL = '/static/'
MEDIA_URL  = '/media/'
MEDIA_ROOT = BASE_DIR / 'media'

LOGIN_URL     = '/accounts/login/'
LOGIN_REDIRECT_URL = '/'

11. Artisan → Manage.py Command Reference