Abílio Azevedo.

Todo List - Django Python

Cover Image for Todo List - Django Python
Abílio Azevedo
Abílio Azevedo

Let's go! First you need to install Python, you can manage multiple versions using pyenv:

brew update
brew install pyenv
pyenv install 3.12.0

Django is a popular open source Python web framework. It was released in 2005 and is maintained by the Django Software Foundation.

  • Based on the model-view-controller (MVC) pattern. This helps keep business logic, presentation logic, and data processing logic separated.
  • Includes an ORM (Object Relational Mapper) that allows easily abstracting and mapping Python objects to databases.
  • Offers a powerful template system based on simple syntax that enables separation between logic and presentation.
  • Includes a ready-to-use user authentication and session management system.
  • Auto-generated site administration available out of the box to easily manage content and users.
  • Large community, many third party packages and good documentation available. To install Django, you can follow the documentation.
> python -m pip install Django
> python -m django --version
4.2.7

Django Rest Framework (DRF) is a popular package that integrates with Django to facilitate building APIs.

  • DRF is built on top of Django and leverages many of its features like the authentication system and ORM.
  • It allows quickly creating scalable web APIs using Django concepts like models and views.
  • Adds features specific to building APIs like data serialization, HTTP request throttling, pagination and rate limiting.
  • Uses generic class-based views to handle common API requests like listing, detailing, creating, deleting and updating data.
  • Provides serializers that translate between complex Python representations and native web representations like JSON.
  • Includes authentication and permission tools specific to APIs.

To manage the packages of our application we will use the package manager called Poetry.

Now let's start our project

mkdir todo_list
cd todo_list

Let's initialize Poetry:

poetry init -n

And add Django, DRF and a package to work with JWT:

poetry add django djangorestframework djangorestframework-simplejwt

Now let's activate the Poetry shell environment:

poetry shell

And we create our project:

django-admin startproject todo_project .

In Django we can have different apps/modules and so we will create our todo tasks (todos) and user management (users) apps

mkdir todo_project/auth
python manage.py startapp todos
python manage.py startapp users

Add the apps and rest_framework to the INSTALLED_APPS array in settings.py

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',   
    'django.contrib.staticfiles',
    'rest_framework', #ADDED 
    'auth', #ADDED
    'users', #ADDED  
]

In this step we will execute the migrations

poetry run python manage.py migrate

You will see that a sqlite database will be created at the root of the project.

And you can run the application with the command:

python manage.py runserver

Now you can access the application:
http://127.0.0.1:8000 Django Start

You can also access the admin panel, but first you need to create a superuser:

poetry run python manage.py createsuperuser

Django Admin http://127.0.0.1:8000/admin

USERS APP

First, let's create a custom User model in case we need to expand the default properties. The models.py file will look like this:

from django.contrib.auth.models import AbstractUser  
from .managers import CustomUserManager
from django.contrib.auth.models import UserManager  

class CustomUserManager(UserManager):
    pass;  

class CustomUser(AbstractUser):    
    objects = CustomUserManager()   

    def __str__(self):
        return f"Username: {self.username} <Email: {self.email}>"

We will have two serializers, one to create the user and another to change the user's password, so create the serializers.py file:

from rest_framework import serializers  
from .models import CustomUser

class RegistrationSerializer(serializers.ModelSerializer): 
    password2 = serializers.CharField(style={"input_type": "password"}, write_only=True)

    class Meta:
        model = CustomUser 
        fields = ['username','email', 'password', 'password2']
        extra_kwargs = {
            'password': {'write_only': True}
        }

    def save(self):
        user = CustomUser(username=self.validated_data['username'],email=self.validated_data['email'])
        password = self.validated_data['password']
        password2 = self.validated_data['password2']
        if password != password2:
            raise serializers.ValidationError({'password': 'Passwords must match.'}) 
        user.set_password(password)
        user.save()
        return user

class PasswordChangeSerializer(serializers.Serializer):
    current_password = serializers.CharField(style={"input_type": "password"}, required=True)
    new_password = serializers.CharField(style={"input_type": "password"}, required=True)

    def validate_current_password(self, value):
        if not self.context['request'].user.check_password(value): 
            raise serializers.ValidationError({'current_password': 'Does not match'})
        return value

In the application user views we will create our user CRUD:

from django.contrib.auth import authenticate, login, logout
from rest_framework import status  
from rest_framework.permissions import IsAuthenticated
from rest_framework.response import  Response
from rest_framework.views import APIView
from .serializers import RegistrationSerializer, PasswordChangeSerializer
from rest_framework_simplejwt.tokens import RefreshToken  

def get_tokens_for_user(user):
    refresh = RefreshToken.for_user(user)   

    return {
        'refresh': str(refresh),
        'access': str(refresh.access_token),
    }  

class RegistrationView(APIView):  
    def post(self, request):
        serializer = RegistrationSerializer(data=request.data)  
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data, status=status.HTTP_201_CREATED)
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

class LoginView(APIView):
    def post(self, request):
        if 'username' not in request.data or 'password' not in request.data:
            return Response({'msg': 'Credentials missing'},          status=status.HTTP_400_BAD_REQUEST)
        username = request.data.get('username')
        password = request.data.get('password')
        user = authenticate(request, username=username, password=password)
        if user is not None:  
            login(request, user)
            auth_data = get_tokens_for_user(request.user)  
            return Response({'msg': 'Login Success', **auth_data}, status=status.HTTP_200_OK)
        return Response({'msg': 'Invalid Credentials'}, status=status.HTTP_401_UNAUTHORIZED)

class LogoutView(APIView):
    def post(self, request): 
        logout(request)
        return Response({'msg': 'Successfully Logged out'}, status=status.HTTP_200_OK)  

class ProfileView(APIView):
    permission_classes = [IsAuthenticated, ] 

    def get(self, request):
        user = request.user
        data = {
            'id': user.id, 
            'username': user.username,
            'first_name': user.first_name,
            'last_name': user.last_name,
            'email': user.email
        }
        return Response(data, status=status.HTTP_200_OK)

class ChangePasswordView(APIView):
    permission_classes = [IsAuthenticated, ]

    def post(self, request):
        serializer = PasswordChangeSerializer(context={'request': request}, data=request.data) 
        serializer.is_valid(raise_exception=True)
        request.user.set_password(serializer.validated_data['new_password'])
        request.user.save()
        return Response(status=status.HTTP_204_NO_CONTENT)

Now let's expose these views in the URLs:

from django.urls import path 
from .views import RegistrationView, LoginView, LogoutView, ChangePasswordView, ProfileView  
from rest_framework_simplejwt import views as jwt_views

app_name = 'users'  

urlpatterns = [
    path('register', RegistrationView.as_view(), name='register'),
    path('login', LoginView.as_view(), name='login'),
    path('me', ProfileView.as_view(), name='profile'), 
    path('logout', LogoutView.as_view(), name='logout'),
    path('change-password', ChangePasswordView.as_view(), name='password'),
    path('token-refresh/', jwt_views.TokenRefreshView.as_view(), name='token_refresh'),  
]

We will also add some authentication settings to the settings.py file in the todo_project folder:

REST_FRAMEWORK = {
    # Use Django&#39;s standard `django.contrib.auth` permissions,
    # or allow read-only access for unauthenticated users.
    &#39;DEFAULT_PERMISSION_CLASSES&#39;: [
        &#39;rest_framework.permissions.AllowAny&#39;
    ],
    &#39;DEFAULT_AUTHENTICATION_CLASSES&#39;: [
        &#39;rest_framework_simplejwt.authentication.JWTAuthentication&#39;,
    ]
}  

SIMPLE_JWT = {
    &#39;ACCESS_TOKEN_LIFETIME&#39;: datetime.timedelta(days=1),
    &#39;REFRESH_TOKEN_LIFETIME&#39;: datetime.timedelta(days=1),  
}

AUTH_PROFILE_MODULE = &#39;users.CustomUser&#39;  

AUTH_USER_MODEL = &#39;users.CustomUser&#39;

TODOS APP

Create the todo model in the models.py file of the todos module:

from django.db import models  

class Todo(models.Model):
    title = models.TextField()
    description = models.TextField(null=True, blank=True)
    date_created = models.DateTimeField(auto_now_add=True)
    date_modified = models.DateTimeField(auto_now=True)
    is_completed = models.BooleanField(default=False)
    owner = models.ForeignKey(  
      'users.CustomUser',
      related_name='todos',
      on_delete=models.CASCADE,
    )   

    def __str__(self):
      return f"Title: {self.title} <Completed: {self.is_completed}>"

Create the serializers.py file:

from rest_framework import serializers
from .models import Todo

class TodoSerializer(serializers.ModelSerializer):
    class Meta:
        fields = (
            'id', 
            'title',
            'description',
            'is_completed',
            'owner',  
        )
        model = Todo

And now let's make the CRUD views for the todos:

from rest_framework import viewsets, status
from rest_framework.response import Response  
from rest_framework.permissions import IsAuthenticated   

from .models import Todo  
from .serializers import TodoSerializer

class TodoViewSet(viewsets.ModelViewSet):
    permission_classes = [IsAuthenticated]
    serializer_class = TodoSerializer  

    def get_queryset(self):
        return Todo.objects.filter(owner=self.request.user)

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

    def destroy(self, request, *args, **kwargs):
        todo = self.get_object()
        if todo.owner == request.user:
            todo.delete() 
            return Response(status=status.HTTP_204_NO_CONTENT)
        else:
            return Response(status=status.HTTP_404_NOT_FOUND)

    def partial_update(self, request, *args, **kwargs):
        todo = self.get_object()
        if todo.owner != request.user:
            return Response(status=status.HTTP_404_NOT_FOUND)

        serializer = self.get_serializer(todo, data=request.data, partial=True)
        serializer.is_valid(raise_exception=True) 
        serializer.save()  

        return Response(serializer.data)

Now we need to generate and run the todo model migration:

poetry run python manage.py makemigrations  
python manage.py migrate

Documentation

Let's add a library to generate our documentation automatically:

poetry add drf-yasg

Add to the settings.py file:

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',  
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'rest_framework',
    'drf_yasg', # ADDED 
    'users',
    'todos',  
]

And our urls.py file will look like this, with the documentation routes:

from django.contrib import admin  
from django.urls import path, include 
from rest_framework import permissions
from drf_yasg.views import get_schema_view
from drf_yasg import openapi  

schema_view = get_schema_view(
    openapi.Info(
        title="Todo API",
        default_version='v1',
        description="Simple todo API", 
        terms_of_service="https://www.google.com/policies/terms/",
        contact=openapi.Contact(email="me@abilioazevedo.com.br"), 
        license=openapi.License(name="BSD License"),
    ),
    public=True,
    permission_classes=(permissions.AllowAny,),  
)  

urlpatterns = [
    path('swagger<format>/', schema_view.without_ui(cache_timeout=0), name='schema-json'),
    path('swagger/', schema_view.with_ui('swagger', cache_timeout=0), name='schema-swagger-ui'),
    path('redoc/', schema_view.with_ui('redoc', cache_timeout=0), name='schema-redoc'),
    path('admin/', admin.site.urls),
    path("api/v1/users/", include("users.urls"), name="users"),
    path("api/v1/", include("todos.urls"), name="todos")  
]

Now just access: http://127.0.0.1:8000/swagger/.
Todo Swagger Python

Deploy it

You can use https://render.com/ to deploy your application, you just need to connect your repository and deploy it using Docker.

You can test it here

Extra Commands

To check for database migrations

poetry run python manage.py showmigrations

If the migration has already been made but Django has not marked it as done, you can perform it falsely:

poetry run python manage.py migrate --fake transactions 0009

Go to a specific migration

poetry run python manage.py migrate app_name 0003

To print some information you can use the function:

print(obj)

Here is the translation to English:

Run the python shell:

poetry run python manage.py shell_plus

Inside the shell we can import and execute files:

from .models import Todo

todo = Todo(title='Create a todo list', description="Using Django")

todo.save()

print(Todo.objects.all())

This opens the Django shell_plus, which allows executing code in the context of the Django project.

Inside the shell, it imports the Todo model, creates a new Todo object, saves it to the database and prints all Todo objects.

The shell_plus is useful for interactively testing and debugging Django code and functionality during development.

Django proxy models

Django proxy models allow you to modify the behavior of an existing model without creating a new database table. Key points:

  1. Purpose: Add methods or change the default manager without altering the database schema.

  2. Usage: Inherit from an existing model and set Meta.proxy = True.

  3. Limitations: Cannot add new fields or change existing ones.

  4. Use cases:

  • Adding custom methods
  • Modifying the default manager
  • Changing model metadata (e.g., default ordering)
  1. Benefits:
  • Code organization
  • Behavior customization without database changes

Example:

from django.db import models

class Person(models.Model):
    name = models.CharField(max_length=100)

class VIPPerson(Person):
    class Meta:
        proxy = True

    def get_vip_status(self):
        return "VIP"

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Experienced Software Engineer with degree in Electrical Engineering with over 10 years of hands-on expertise in building robust and scalable mobile, web and backend applications across various projects mainly in the fintech sector. Mobile (React Native), Web (React and Next.JS) and Backend (Node.JS, PHP and DJANGO). My goal is to create products that add value to people. - © 2024, Abílio Azevedo

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