Django REST framework: Build an API in 15 minutes

Django REST framework (DRF) is a powerful and flexible toolkit for building web APIs. In this guide, we’ll show you how to build a CRUD API in just 15 minutes using the Django REST framework.

We’ll cover the following:

• What is Django?
• What is a REST API?
• What is Django REST framework?
• Setting up Django REST framework
• RESTful structure
• Creating models for our Django app
• Creating API views in Django: List view and detail view

To demonstrate, we’ll build a CRUD API for a sample to-do application. We’ll start by setting up the Django REST framework in a Django project, followed by a complete tutorial on how to create a CRUD REST API with the Django REST framework.

What is Django?

Django is a Python-based, free, open-source web framework that follows the model-template-views architectural pattern. It reduces the hassle associated with web development so you can focus on writing your app instead of reinventing the wheel.

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, such as JSON, images, HTML etc.

What is 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 such as class-based views, forms, model validator, QuerySet, etc.

Setting up Django REST framework

Start by installing the Django and Django REST framework in your project.

pip install django
pip install django_rest_framework

Create an app called todo with the following command:

python manage.py startapp todo

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

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# 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'
]

Create an api folder and add new files as configured in the directory structure below:

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

Also, include rest_framework and URLs as shown below in your main urls.py file:

# drf_guide/urls.py : Main urls.py
from django.conf.urls import url
from django.urls import path, include
from django.contrib import admin

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

Create a superuser. We’ll get back to this later.

python manage.py createsuperuser

Also, include the API URLs inside the todo urls.py.

# todo/urls.py : App urls.py
from django.conf.urls import url
from django.urls import path, include

urlpatterns = [
    path('api/', include('todo.api.urls')),
]

RESTful structure

In a RESTful API, endpoints define the structure and usage with the following HTTP methods:

• GET
• POST
• PUT
• DELETE

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. We’ll use two endpoints with their respective HTTP methods, as shown in the table below:

Creating models for our Django app

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

# todo/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 such as JSON, Django REST framework uses the ModelSerializer class to convert any model to serialized JSON object.

# todo/api/serializers.py
from rest_framework import serializers
from todo.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 have added permission_classes, which allows authenticated users only.

# 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 todo.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)

What are these methods doing?

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 above class-based view:

# 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('', TodoListApiView.as_view()),
]

Run the Django server:

python manage.py runserver

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

You can create a new to-do by posting:

{
    "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, 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
        )

What are these methods doing?

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

Now if you navigate to http://127.0.0.1:8000/todos/api/<id>/, it will show up the detail API view page. Notice that you correctly navigate to a valid ID. For the below screenshot, 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. Have fun building some new APIs using the Django REST framework!

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