Tag: Django Rest Framework Cheat Sheet

Install the package via pip:

$ pip install djangorestframework

Then, add 'rest_framework' to INSTALLED_APPS in your settings.py file.

INSTALLED_APPS = [
    # Rest of your installed apps ...
    'rest_framework',
]

Serializers allow complex data like querysets and model instances to be converted to native Python datatypes that can then be easily rendered into JSON, XML, and other formats.

Using ModelSerializer class:

Suppose we wanted to create a PostSerializer for our example Post model and CommentSerializer for our Comment model.

class PostSerializer(serializers.ModelSerializer):

    class Meta:
        model = Post
        fields = ('id', 'title', 'text', 'created')
        
        
class CommentSerializer(serializers.ModelSerializer):

    class Meta:
        model = Comment
        fields = ('post', 'user', 'text')

Or also you could use exclude to exclude certain fields from being seialized. ModelSerializer has default implementations for the create() and update() methods.

Nested Serialization

By default, instances are serialized with primary keys to represent relationships. To get nested serialization we could use, General or Explicit methods.

General

Using depth parameter.

class CommentSerializer(serializers.ModelSerializer):

    class Meta:
        model = Comment
        fields = '__all__'
        depth = 2

Explicit

Yuo can also define and nest serializers within eachother…

class CommentSerializer(serializers.ModelSerializer):
    post = PostSerializer()
    
    class Meta:
        model = Comment
        fields = '__all__'

So here, the comment’s post field (how we named it in models.py) will serialize however we defined it in PostSerializer.

HyperlinkedModelSerializer

This makes your web API a lot more easy to use (in browser) and would be a nice feature to add.

Let’s say we wanted to see the comments that every post has in each of the Post instances of our API.

With HyperlinkedModelSerializer, instead of having nested primary keys or nested fields, we get a link to each individual Comment (URL).

class PostSerializer(serializers.HyperlinkedModelSerializer):

    class Meta:
        model = Post
        fields = ('id', 'title', 'text', 'created', 'comments')
        read_only_fields = ('comments',)

Note: without the read_only_fields, the create form for Posts would always require a comments input, which doesn’t make sense (comments on a post are normally made AFTER the post is created).

Another way of hyperlinking is just adding a HyperlinkedRelatedField definition to a normal serializer.

class PostSerializer(serializers.ModelSerializer):
    comments = serializers.HyperlinkedRelatedField(many=True, view_name='comment-detail', read_only=True)
    
    class Meta:
        model = Post
        fields = ('id', 'title', 'text', 'created', 'comments')

Dynamically modifying fields in the serializer

This makes your web API a lot more easy for extract limited number of parameter in response. Let’s say you want to set which fields should be used by a serializer at the point of initialization.

Just copy below code and past it in your serliazer file

class DynamicFieldsModelSerializer(serializers.ModelSerializer):

    def __init__(self, *args, **kwargs):
        # Don't pass the 'fields' arg up to the superclass
        fields = kwargs.pop('fields', None)

        # Instantiate the superclass normally
        super(DynamicFieldsModelSerializer, self).__init__(*args, **kwargs)

        if fields is not None:
            # Drop any fields that are not specified in the `fields` argument.
            allowed = set(fields)
            existing = set(self.fields.keys())
            for field_name in existing - allowed:
                self.fields.pop(field_name)

Extend DynamicFieldsModelSerializer from your serializer class

class UserSerializer(DynamicFieldsModelSerializer):
    class Meta:
        model = User
        fields = ('id', 'username', 'email')

Mention the fields name inside fields

UserSerializer(user, fields=('id', 'email'))

Here, you will get only id and email from serializer instead of all.

There are many options for creating views for your web API, it really depends on what you want and personal preference.

Using Function-based views:

from rest_framework.decorators import api_view
from rest_framework.response import Response
from rest_framework.parsers import JSONParser
from rest_framework import status
from posts.models import Post
from posts.serializers import PostSerializer

@api_view(['GET', 'POST'])
def post_list(request, format=None):

    if request.method == 'GET':
        posts = Post.objects.all()
        serializer = PostSerializer(posts, many=True)
        return Response(serializer.data)

    elif request.method == 'POST':
        data = JSONParser().parse(request)
        serializer = PostSerializer(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)

Using Class-based views:

from rest_framework.response import Response
from rest_framework import status
from rest_framework.views import APIView
from posts.models import Post
from posts.serializers import PostSerializer


class PostList(APIView):
    def get(self, request, format=None):
        snippets = Post.objects.all()
        serializer = PostSerializer(snippets, many=True)
        return Response(serializer.data)

    def post(self, request, format=None):
        serializer = PostSerializer(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)

Using Generic Class-based views:

from rest_framework import generics
from posts.models import Post
from posts.serializers import PostSerializer


class PostList(generics.ListCreateAPIView):
    queryset = Post.objects.all()
    serializer_class = PostSerializer

Using Mixins:

from rest_framework import generics, mixins
from posts.models import Post
from posts.serializers import PostSerializer


class PostList(generics.GenericAPIView,
               mixins.ListModelMixin,
               mixins.CreateModelMixin
               ):
    queryset = Post.objects.all()
    serializer_class = PostSerializer

    def get(self, request, *args, **kwargs):
        return self.list(request, *args, **kwargs)

    def post(self, request, *args, **kwargs):
        return self.create(request, *args, **kwargs)

Using ViewSets:

With ModelViewSet (in this case), you don’t have to create separate views for getting list of objects and detail of one object. ViewSet will handle it for you in a consistent way for both methods.

from rest_framework import viewsets
from posts.models import Post
from posts.serializers import PostSerializer


class PostViewSet(viewsets.ModelViewSet):
    """
    A viewset for viewing and editing post instances.
    """
    queryset = Post.objects.all()
    serializer_class = PostSerializer

Routers

Routers in ViewSets allow the URL configuration for your API to be automatically generated using naming standards.

from rest_framework.routers import DefaultRouter
from posts.views import PostViewSet

router = DefaultRouter()
router.register(r'users', UserViewSet)
urlpatterns = router.urls

Custom Actions in ViewSets

DRF provides helpers to add custom actions for ad-hoc behaviours with the @action decorator. The router will configure its url accordingly. For example, we can add a comments action in the our PostViewSet to retrieve all the comments of a specific post as follows:

from rest_framework import viewsets
from rest_framework.decorators import action
from posts.models import Post
from posts.serializers import PostSerializer, CommentSerializer


class PostViewSet(viewsets.ModelViewSet):
   ...
   
   @action(methods=['get'], detail=True)
   def comments(self, request, pk=None):
       try:
           post = Post.objects.get(id=pk)
       except Post.DoesNotExist:
           return Response({"error": "Post not found."},
                           status=status.HTTP_400_BAD_REQUEST)
       comments = post.comments.all()
       return Response(CommentSerializer(comments, many=True))

Upon registering the view as router.register(r'posts', PostViewSet), this action will then be available at the url posts/{pk}/comments/.