This tutorial will cover creating a simple pastebin code highlighting Web API. Along the way it will introduce the various components that make up REST framework, and give you a comprehensive understanding of how everything fits together.

The tutorial is fairly in-depth, so you should probably get a cookie and a cup of your favorite brew before getting started. If you just want a quick overview, you should head over to thequickstart documentation instead.

Note: The code for this tutorial is available in theencode/rest-framework-tutorial repository on GitHub. Feel free to clone the repository and see the code in action.

Setting up a new environment

Before we do anything else we'll create a new virtual environment, usingvenv. This will make sure our package configuration is kept nicely isolated from any other projects we're working on.

python3 -m venv envsource env/bin/activate

Now that we're inside a virtual environment, we can install our package requirements.

pip install djangopip install djangorestframeworkpip install pygments  # We'll be using this for the code highlighting

Note: To exit the virtual environment at any time, just typedeactivate. For more information see thevenv documentation.

Getting started

Okay, we're ready to get coding.To get started, let's create a new project to work with.

cd ~django-admin startproject tutorialcd tutorial

Once that's done we can create an app that we'll use to create a simple Web API.

python manage.py startapp snippets

We'll need to add our newsnippets app and therest_framework app toINSTALLED_APPS. Let's edit thetutorial/settings.py file:

INSTALLED_APPS = [    ...    'rest_framework',    'snippets',]

Okay, we're ready to roll.

Creating a model to work with

For the purposes of this tutorial we're going to start by creating a simpleSnippet model that is used to store code snippets. Go ahead and edit thesnippets/models.py file. Note: Good programming practices include comments. Although you will find them in our repository version of this tutorial code, we have omitted them here to focus on the code itself.

from django.db import modelsfrom pygments.lexers import get_all_lexersfrom pygments.styles import get_all_stylesLEXERS = [item for item in get_all_lexers() if item[1]]LANGUAGE_CHOICES = sorted([(item[1][0], item[0]) for item in LEXERS])STYLE_CHOICES = sorted([(item, item) for item in get_all_styles()])class Snippet(models.Model):    created = models.DateTimeField(auto_now_add=True)    title = models.CharField(max_length=100, blank=True, default="")    code = models.TextField()    linenos = models.BooleanField(default=False)    language = models.CharField(        choices=LANGUAGE_CHOICES, default="python", max_length=100    )    style = models.CharField(choices=STYLE_CHOICES, default="friendly", max_length=100)    class Meta:        ordering = ["created"]

We'll also need to create an initial migration for our snippet model, and sync the database for the first time.

python manage.py makemigrations snippetspython manage.py migrate snippets

Creating a Serializer class

The first thing we need to get started on our Web API is to provide a way of serializing and deserializing the snippet instances into representations such asjson. We can do this by declaring serializers that work very similar to Django's forms. Create a file in thesnippets directory namedserializers.py and add the following.

from rest_framework import serializersfrom snippets.models import Snippet, LANGUAGE_CHOICES, STYLE_CHOICESclass SnippetSerializer(serializers.Serializer):    id = serializers.IntegerField(read_only=True)    title = serializers.CharField(required=False, allow_blank=True, max_length=100)    code = serializers.CharField(style={"base_template": "textarea.html"})    linenos = serializers.BooleanField(required=False)    language = serializers.ChoiceField(choices=LANGUAGE_CHOICES, default="python")    style = serializers.ChoiceField(choices=STYLE_CHOICES, default="friendly")    def create(self, validated_data):        """        Create and return a new `Snippet` instance, given the validated data.        """        return Snippet.objects.create(**validated_data)    def update(self, instance, validated_data):        """        Update and return an existing `Snippet` instance, given the validated data.        """        instance.title = validated_data.get("title", instance.title)        instance.code = validated_data.get("code", instance.code)        instance.linenos = validated_data.get("linenos", instance.linenos)        instance.language = validated_data.get("language", instance.language)        instance.style = validated_data.get("style", instance.style)        instance.save()        return instance

The first part of the serializer class defines the fields that get serialized/deserialized. Thecreate() andupdate() methods define how fully fledged instances are created or modified when callingserializer.save()

A serializer class is very similar to a DjangoForm class, and includes similar validation flags on the various fields, such asrequired,max_length anddefault.

The field flags can also control how the serializer should be displayed in certain circumstances, such as when rendering to HTML. The{'base_template': 'textarea.html'} flag above is equivalent to usingwidget=widgets.Textarea on a DjangoForm class. This is particularly useful for controlling how the browsable API should be displayed, as we'll see later in the tutorial.

We can actually also save ourselves some time by using theModelSerializer class, as we'll see later, but for now we'll keep our serializer definition explicit.

Working with Serializers

Before we go any further we'll familiarize ourselves with using our new Serializer class. Let's drop into the Django shell.

python manage.py shell

Okay, once we've got a few imports out of the way, let's create a couple of code snippets to work with.

>>> from snippets.models import Snippet>>> from snippets.serializers import SnippetSerializer>>> from rest_framework.renderers import JSONRenderer>>> from rest_framework.parsers import JSONParser>>> snippet = Snippet(code='foo = "bar"\n')>>> snippet.save()>>> snippet = Snippet(code='print("hello, world")\n')>>> snippet.save()

We've now got a few snippet instances to play with. Let's take a look at serializing one of those instances.

>>> serializer = SnippetSerializer(snippet)>>> serializer.data{'id': 2, 'title': '', 'code': 'print("hello, world")\n', 'linenos': False, 'language': 'python', 'style': 'friendly'}

At this point we've translated the model instance into Python native datatypes. To finalize the serialization process we render the data intojson.

>>> content = JSONRenderer().render(serializer.data)>>> contentb'{"id":2,"title":"","code":"print(\\"hello, world\\")\\n","linenos":false,"language":"python","style":"friendly"}'

Deserialization is similar. First we parse a stream into Python native datatypes...

>>> import io>>> stream = io.BytesIO(content)>>> data = JSONParser().parse(stream)

...then we restore those native datatypes into a fully populated object instance.

>>> serializer = SnippetSerializer(data=data)>>> serializer.is_valid()True>>> serializer.validated_data{'title': '', 'code': 'print("hello, world")', 'linenos': False, 'language': 'python', 'style': 'friendly'}>>> serializer.save()<Snippet: Snippet object>

Notice how similar the API is to working with forms. The similarity should become even more apparent when we start writing views that use our serializer.

We can also serialize querysets instead of model instances. To do so we simply add amany=True flag to the serializer arguments.

>>> serializer = SnippetSerializer(Snippet.objects.all(), many=True)>>> serializer.data[{'id': 1, 'title': '', 'code': 'foo = "bar"\n', 'linenos': False, 'language': 'python', 'style': 'friendly'}, {'id': 2, 'title': '', 'code': 'print("hello, world")\n', 'linenos': False, 'language': 'python', 'style': 'friendly'}, {'id': 3, 'title': '', 'code': 'print("hello, world")', 'linenos': False, 'language': 'python', 'style': 'friendly'}]

Using ModelSerializers

OurSnippetSerializer class is replicating a lot of information that's also contained in theSnippet model. It would be nice if we could keep our code a bit more concise.

In the same way that Django provides bothForm classes andModelForm classes, REST framework includes bothSerializer classes, andModelSerializer classes.

Let's look at refactoring our serializer using theModelSerializer class.Open the filesnippets/serializers.py again, and replace theSnippetSerializer class with the following.

class SnippetSerializer(serializers.ModelSerializer):    class Meta:        model = Snippet        fields = ["id", "title", "code", "linenos", "language", "style"]

One nice property that serializers have is that you can inspect all the fields in a serializer instance, by printing its representation. Open the Django shell withpython manage.py shell, then try the following:

>>> from snippets.serializers import SnippetSerializer>>> serializer = SnippetSerializer()>>> print(repr(serializer))SnippetSerializer():    id = IntegerField(label='ID', read_only=True)    title = CharField(allow_blank=True, max_length=100, required=False)    code = CharField(style={'base_template': 'textarea.html'})    linenos = BooleanField(required=False)    language = ChoiceField(choices=[('Clipper', 'FoxPro'), ('Cucumber', 'Gherkin'), ('RobotFramework', 'RobotFramework'), ('abap', 'ABAP'), ('ada', 'Ada')...    style = ChoiceField(choices=[('autumn', 'autumn'), ('borland', 'borland'), ('bw', 'bw'), ('colorful', 'colorful')...

It's important to remember thatModelSerializer classes don't do anything particularly magical, they are simply a shortcut for creating serializer classes:

An automatically determined set of fields.
Simple default implementations for thecreate() andupdate() methods.

Writing regular Django views using our Serializer

Let's see how we can write some API views using our new Serializer class.For the moment we won't use any of REST framework's other features, we'll just write the views as regular Django views.

Edit thesnippets/views.py file, and add the following.

from django.http import HttpResponse, JsonResponsefrom django.views.decorators.csrf import csrf_exemptfrom rest_framework.parsers import JSONParserfrom snippets.models import Snippetfrom snippets.serializers import SnippetSerializer

The root of our API is going to be a view that supports listing all the existing snippets, or creating a new snippet.

@csrf_exemptdef snippet_list(request):    """    List all code snippets, or create a new snippet.    """    if request.method == "GET":        snippets = Snippet.objects.all()        serializer = SnippetSerializer(snippets, many=True)        return JsonResponse(serializer.data, safe=False)    elif request.method == "POST":        data = JSONParser().parse(request)        serializer = SnippetSerializer(data=data)        if serializer.is_valid():            serializer.save()            return JsonResponse(serializer.data, status=201)        return JsonResponse(serializer.errors, status=400)

Note that because we want to be able to POST to this view from clients that won't have a CSRF token we need to mark the view ascsrf_exempt. This isn't something that you'd normally want to do, and REST framework views actually use more sensible behavior than this, but it'll do for our purposes right now.

We'll also need a view which corresponds to an individual snippet, and can be used to retrieve, update or delete the snippet.

@csrf_exemptdef snippet_detail(request, pk):    """    Retrieve, update or delete a code snippet.    """    try:        snippet = Snippet.objects.get(pk=pk)    except Snippet.DoesNotExist:        return HttpResponse(status=404)    if request.method == "GET":        serializer = SnippetSerializer(snippet)        return JsonResponse(serializer.data)    elif request.method == "PUT":        data = JSONParser().parse(request)        serializer = SnippetSerializer(snippet, data=data)        if serializer.is_valid():            serializer.save()            return JsonResponse(serializer.data)        return JsonResponse(serializer.errors, status=400)    elif request.method == "DELETE":        snippet.delete()        return HttpResponse(status=204)

Finally we need to wire these views up. Create thesnippets/urls.py file:

from django.urls import pathfrom snippets import viewsurlpatterns = [    path("snippets/", views.snippet_list),    path("snippets/<int:pk>/", views.snippet_detail),]

We also need to wire up the root urlconf, in thetutorial/urls.py file, to include our snippet app's URLs.

from django.urls import path, includeurlpatterns = [    path("", include("snippets.urls")),]

It's worth noting that there are a couple of edge cases we're not dealing with properly at the moment. If we send malformedjson, or if a request is made with a method that the view doesn't handle, then we'll end up with a 500 "server error" response. Still, this'll do for now.

Testing our first attempt at a Web API

Now we can start up a sample server that serves our snippets.

Quit out of the shell...

>>> quit()

...and start up Django's development server.

python manage.py runserverValidating models...0 errors foundDjango version 5.0, using settings 'tutorial.settings'Starting Development server at http://127.0.0.1:8000/Quit the server with CONTROL-C.

In another terminal window, we can test the server.

We can test our API usingcurl orhttpie. Httpie is a user friendly http client that's written in Python. Let's install that.

You can install httpie using pip:

pip install httpie

Finally, we can get a list of all of the snippets:

http GET http://127.0.0.1:8000/snippets/ --unsortedHTTP/1.1 200 OK...[    {        "id": 1,        "title": "",        "code": "foo = \"bar\"\n",        "linenos": false,        "language": "python",        "style": "friendly"    },    {        "id": 2,        "title": "",        "code": "print(\"hello, world\")\n",        "linenos": false,        "language": "python",        "style": "friendly"    },    {        "id": 3,        "title": "",        "code": "print(\"hello, world\")",        "linenos": false,        "language": "python",        "style": "friendly"    }]

Or we can get a particular snippet by referencing its id:

http GET http://127.0.0.1:8000/snippets/2/ --unsortedHTTP/1.1 200 OK...{    "id": 2,    "title": "",    "code": "print(\"hello, world\")\n",    "linenos": false,    "language": "python",    "style": "friendly"}

Similarly, you can have the same json displayed by visiting these URLs in a web browser.

Where are we now

We're doing okay so far, we've got a serialization API that feels pretty similar to Django's Forms API, and some regular Django views.

Our API views don't do anything particularly special at the moment, beyond servingjson responses, and there are some error handling edge cases we'd still like to clean up, but it's a functioning Web API.

We'll see how we can start to improve things inpart 2 of the tutorial.

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Tutorial 1: Serialization

Introduction