How to create a REST API with Django REST framework

What is a REST API?

A REST API is a popular way for systems to expose useful functions and data. REST, which stands for representational state transfer, can be made up of one or more resources that can be accessed at a given URL and returned in various formats, like JSON, images, HTML, and more.

Why Django REST framework?

Django REST framework (DRF) is a powerful and flexible toolkit for building Web APIs. Its main benefit is that it makes serialization much easier.

Django REST framework is based on Django’s class-based views, so it’s an excellent option if you’re familiar with Django. It adopts implementations like class-based views, forms, model validator, QuerySet, and more.

Setting up Django REST framework

Ideally, you’d want to create a virtual environment to isolate dependencies, however, this is optional. Run the command:

python -m venv django_env

from inside your projects folder to create the virtual environment. Then, run this command to turn it on.

source ./django_env/bin/activate

Keep in mind that you’ll need to reactivate your virtual environment in every new terminal session. You’ll know that it is turned on because the environment’s name will become part of the shell prompt.

Navigate to an empty folder in your terminal and install Django and Django REST framework in your project with the commands below:

pip install django
pip install django_rest_framework

Create a Django project called todo with the following command:

django-admin startproject todo

Then, cd into the new todo folder and create a new app for your API:

django-admin startapp todo_api

Run your initial migrations of the built-in user model:

python manage.py migrate

Next, add rest_framework and todo to the INSTALLED_APPS inside the todo/todo/settings.py file:

# settings.py
INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'rest_framework',
    'todo_api'
]

Create a serializers.py and urls.py file in todo/todo_api and add new files as configured in the directory structure below:

├── todo
│   ├── __init__.py
│   ├── settings.py
│   ├── urls.py
├── db.sqlite3
├── manage.py
└── todo_api
    ├── admin.py
    ├── serializers.py
    ├── __init__.py
    ├── models.py
    ├── urls.py
    └── views.py

Be sure to include rest_framework and URLs as shown below in your main urls.py file:

# todo/todo/urls.py : Main urls.py
from django.contrib import admin
from django.urls import path, include
from todo_api import urls as todo_urls

urlpatterns = [
    path('admin/', admin.site.urls),
    path('api-auth/', include('rest_framework.urls')),
    path('todos/', include(todo_urls)),
]

Next, create a superuser. We’ll come back to this later:

python manage.py createsuperuser

---

RESTful structure: GET, POST, PUT, and DELETE methods

In a RESTful API, endpoints define the structure and usage with the GET, POST, PUT, and DELETE HTTP methods. You must organize these methods logically.

To show how to build a RESTful app with Django REST framework, we’ll create an example to-do API.

Creating models for our Django app

Let’s start by creating the model for our to-do list:

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

class Todo(models.Model):
    task = models.CharField(max_length = 180)
    timestamp = models.DateTimeField(auto_now_add = True, auto_now = False, blank = True)
    completed = models.BooleanField(default = False, blank = True)
    updated = models.DateTimeField(auto_now = True, blank = True)
    user = models.ForeignKey(User, on_delete = models.CASCADE, blank = True, null = True)

    def __str__(self):
        return self.task

After creating the model, migrate it to the database.

python manage.py makemigrations
python manage.py migrate

Model serializer

To convert the Model object to an API-appropriate format like JSON, Django REST framework uses the ModelSerializer class to convert any model to serialized JSON objects:

# todo/todo_api/serializers.py
from rest_framework import serializers
from .models import Todo
class TodoSerializer(serializers.ModelSerializer):
    class Meta:
        model = Todo
        fields = ["task", "completed", "timestamp", "updated", "user"]

Creating API views in Django

In this section, we’ll walk through how to create two API views, list view and detail view.

List view

The first API view class deals with the todos/api/ endpoint, in which it handles GET for listing all to-dos of a given requested user and POST for creating a new to-do. Notice that we’ve added permission_classes, which allows authenticated users only:

# todo/todo_api/views.py
from rest_framework.views import APIView
from rest_framework.response import Response
from rest_framework import status
from rest_framework import permissions
from .models import Todo
from .serializers import TodoSerializer

class TodoListApiView(APIView):
    # add permission to check if user is authenticated
    permission_classes = [permissions.IsAuthenticated]

    # 1. List all
    def get(self, request, *args, **kwargs):
        '''
        List all the todo items for given requested user
        '''
        todos = Todo.objects.filter(user = request.user.id)
        serializer = TodoSerializer(todos, many=True)
        return Response(serializer.data, status=status.HTTP_200_OK)

    # 2. Create
    def post(self, request, *args, **kwargs):
        '''
        Create the Todo with given todo data
        '''
        data = {
            'task': request.data.get('task'), 
            'completed': request.data.get('completed'), 
            'user': request.user.id
        }
        serializer = TodoSerializer(data=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)

• The GET() method first fetches all the objects from the model by filtering with the requested user ID.

• Then, it serializes from the model object to a JSON serialized object.

• Next, it returns the response with serialized data and status as 200_OK.

• The POST() method fetches the requested data and adds the requested user ID in the data dictionary.

• Next, it creates a serialized object and saves the object if it’s valid.

• If valid, it returns the serializer.data, which is a newly created object with status as 201_CREATED.

• Otherwise, it returns the serializer.errors with status as 400_BAD_REQUEST.

Create an endpoint for the class-based view above:

# todo/todo_api/urls.py : API urls.py
from django.conf.urls import url
from django.urls import path, include
from .views import (
    TodoListApiView,
)

urlpatterns = [
    path('api', TodoListApiView.as_view()),
]

Run the Django server:

python manage.py runserver

Now, we’re ready for the first test. Navigate to http://127.0.0.1:8000/todos/api. Make sure you’re logged in with your superuser credentials:

You can create a new to-do by posting the following:

{
    "task": "New Task",
    "completed": false
}

Detail view

Now that we’ve successfully created our first endpoint view, let’s create the second endpoint todos/api/<int:todo_id> API view.

In this API view class, we need to create three methods for handling the corresponding HTTP methods, GET, PUT, and DELETE, as discussed above:

# todo/api/views.py
from rest_framework.views import APIView
from rest_framework.response import Response
from rest_framework import status
from todo.models import Todo
from .serializers import TodoSerializer
from rest_framework import permissions

class TodoDetailApiView(APIView):
    # add permission to check if user is authenticated
    permission_classes = [permissions.IsAuthenticated]

    def get_object(self, todo_id, user_id):
        '''
        Helper method to get the object with given todo_id, and user_id
        '''
        try:
            return Todo.objects.get(id=todo_id, user = user_id)
        except Todo.DoesNotExist:
            return None

    # 3. Retrieve
    def get(self, request, todo_id, *args, **kwargs):
        '''
        Retrieves the Todo with given todo_id
        '''
        todo_instance = self.get_object(todo_id, request.user.id)
        if not todo_instance:
            return Response(
                {"res": "Object with todo id does not exists"},
                status=status.HTTP_400_BAD_REQUEST
            )

        serializer = TodoSerializer(todo_instance)
        return Response(serializer.data, status=status.HTTP_200_OK)

    # 4. Update
    def put(self, request, todo_id, *args, **kwargs):
        '''
        Updates the todo item with given todo_id if exists
        '''
        todo_instance = self.get_object(todo_id, request.user.id)
        if not todo_instance:
            return Response(
                {"res": "Object with todo id does not exists"}, 
                status=status.HTTP_400_BAD_REQUEST
            )
        data = {
            'task': request.data.get('task'), 
            'completed': request.data.get('completed'), 
            'user': request.user.id
        }
        serializer = TodoSerializer(instance = todo_instance, data=data, partial = True)
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data, status=status.HTTP_200_OK)
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

    # 5. Delete
    def delete(self, request, todo_id, *args, **kwargs):
        '''
        Deletes the todo item with given todo_id if exists
        '''
        todo_instance = self.get_object(todo_id, request.user.id)
        if not todo_instance:
            return Response(
                {"res": "Object with todo id does not exists"}, 
                status=status.HTTP_400_BAD_REQUEST
            )
        todo_instance.delete()
        return Response(
            {"res": "Object deleted!"},
            status=status.HTTP_200_OK
        )

The GET() method first fetches the object with the ID todo_id and user as request user from the to-do model.

• If the requested object is not available, it returns the response with the status as 400_BAD_REQUEST.

• Otherwise, it serializes the model object to a JSON serialized object and returns the response with serializer.data and status as 200_OK.

The PUT() method fetches the to-do object if it is available in the database, updates its data with requested data, and saves the updated data in the database.

The DELETE() method fetches the to-do object if is available in the database, deletes it, and responds with a response.

Update the API urls.py as demonstrated below:

# todo/api/urls.py : API urls.py
from django.conf.urls import url
from django.urls import path, include
from .views import (
    TodoListApiView,
    TodoDetailApiView
)

urlpatterns = [
    path('api', TodoListApiView.as_view()),
    path('api/<int:todo_id>/', TodoDetailApiView.as_view()),
]

Now, if you navigate to http://127.0.0.1:8000/todos/api/<id>/, it will show the detail API view page. Notice that you correctly navigate to a valid ID. In the screenshot below, I used 7 as the ID:

Conclusion

Congratulations! You’ve successfully built your first fully functional CRUD Django REST API.

Building a RESTful API can be complicated, but Django REST framework handles complexity fairly well. I hope you have fun building new APIs using the Django REST framework, and be sure to leave a comment if you have any questions. Happy coding!