What You Should Know About Django REST Framework

When I started writing Django REST Framework code in 2017, there was a lot I didn't know, like how class-based views worked and what a serializer was.

After 3+ years of using DRF, I want to share the things I've learned that make writing DRF code easier and faster for me. You will learn how to save time and lines of code by using DRF's built-in viewsets (and what a viewset is), when to skip the viewset and use a built-in generic `APIView`, and how to add custom endpoints (actions) to your viewsets. You'll also learn how modular DRF can be when you customize built-in methods or use different serializers for different parts of your viewset, and how tools like Classy DRF can help.

You will walk away from this talk ready to start your first DRF project, make your existing projects simpler and cleaner, or (at the very least) with a better understanding of how a class-based view works.

You will get the most out of this talk if you have beginner-level experience in Python and Django. A tenuous, vague understanding of how class-based views in Django work would be helpful, but is not necessary. Having completed a Django REST Framework tutorial would also be helpful.

Transcript

1. What You Should Know About Django REST Framework Lacey Williams Henschel PyCascades, February 2021 @laceynwilliams | @revsys
2. What You Should Know About Django REST Framework: ViewSets Edition! @laceynwilliams | @revsys
3. ClassyDRF @laceynwilliams | @revsys
4. @laceynwilliams | @revsys
5. @laceynwilliams | @revsys
6. DRF has good docs DRF Docs on ViewSets @laceynwilliams | @revsys
7. ModelViewSet @laceynwilliams | @revsys
8. ModelViewSet = set of views to: ✓ create ✓ retrieve ✓ update ✓ list ✓ destroy @laceynwilliams | @revsys
9. class ModelViewSet(mixins.CreateModelMixin, mixins.RetrieveModelMixin, mixins.UpdateModelMixin, mixins.DestroyModelMixin, mixins.ListModelMixin, GenericViewSet): """ A viewset that provides default `create()`, `retrieve()`, `update()`, `partial_update()`, `destroy()` and `list()` actions. """ pass @laceynwilliams | @revsys
10. Each *ModelMixin class has its own methods that perform the right ac4ons. CreateModelMixin has a create() method, instead of a post() method. @laceynwilliams | @revsys
11. This ViewSet... # views.py from rest_framework.viewsets import ModelViewSet from .models import Book from .serializers import BookSerializer class BookViewSet(ModelViewSet): queryset = Book.objects.all() serializer_class = BookSerializer @laceynwilliams | @revsys
12. ...gives us these endpoints1 GET /books/ GET /books/{id}/ POST /books/ PUT /books/{id}/ PATCH /books/{id}/ DELETE /books/{id}/ 1 you also need to hook the ViewSet to your urls @laceynwilliams | @revsys
13. A"ributes for your ModelViewSet @laceynwilliams | @revsys
14. What objects are you working with? from rest_framework.permissions import AllowAny from rest_framework.viewsets import ModelViewSet from .models import Book from .serializers import BookSerializer class BookViewSet(ModelViewSet): queryset = Book.objects.all() serializer_class = BookSerializer permission_classes = [AllowAny] @laceynwilliams | @revsys
15. How should the data be serialized? from rest_framework.permissions import AllowAny from rest_framework.viewsets import ModelViewSet from .models import Book from .serializers import BookSerializer class BookViewSet(ModelViewSet): queryset = Book.objects.all() serializer_class = BookSerializer permission_classes = [AllowAny] @laceynwilliams | @revsys
16. Who is allowed? from rest_framework.permissions import AllowAny from rest_framework.viewsets import ModelViewSet from .models import Book from .serializers import BookSerializer class BookViewSet(ModelViewSet): queryset = Book.objects.all() serializer_class = BookSerializer permission_classes = [AllowAny] @laceynwilliams | @revsys
17. Methods that come from GenericAPIView @laceynwilliams | @revsys
18. def get_queryset(self): assert self.queryset is not None, ( "'%s' should either include a `queryset` attribute, " "or override the `get_queryset()` method." % self.__class__.__name__ ) queryset = self.queryset if isinstance(queryset, QuerySet): queryset = queryset.all() return queryset @laceynwilliams | @revsys
19. When to override get_queryset(): When you need to filter your queryset with data you don't have un5l the 5me of the request (like filter by user) @laceynwilliams | @revsys
20. def get_object(self): queryset = self.filter_queryset(self.get_queryset()) lookup_url_kwarg = self.lookup_url_kwarg or self.lookup_field assert lookup_url_kwarg in self.kwargs, ( 'Expected view %s to be called with a URL keyword argument ' 'named "%s". Fix your URL conf, or set the `.lookup_field` ' 'attribute on the view correctly.' % (self.__class__.__name__, lookup_url_kwarg) ) # Uses the lookup_field attribute, which defaults to `pk` filter_kwargs = {self.lookup_field: self.kwargs[lookup_url_kwarg]} obj = get_object_or_404(queryset, **filter_kwargs) # May raise a permission denied self.check_object_permissions(self.request, obj) return obj @laceynwilliams | @revsys
21. In your own methods, you can run: obj = self.get_object() instead of looking up the object yourself. @laceynwilliams | @revsys
22. def get_serializer_class(self): assert self.serializer_class is not None, ( "'%s' should either include a `serializer_class` attribute, " "or override the `get_serializer_class()` method." % self.__class__.__name__ ) # Returns the attribute you set return self.serializer_class @laceynwilliams | @revsys
23. When to override get_serializer_class(): When you want to use different serializers in different situa3ons @laceynwilliams | @revsys
24. def get_serializer(self, *args, **kwargs): serializer_class = self.get_serializer_class() # The context is where the request is added # to the serializer kwargs['context'] = self.get_serializer_context() return serializer_class(*args, **kwargs) @laceynwilliams | @revsys
25. def get_serializer(self, *args, **kwargs): serializer_class = self.get_serializer_class() # The context is where the request is added # to the serializer kwargs['context'] = self.get_serializer_context() return serializer_class(*args, **kwargs) @laceynwilliams | @revsys
26. def get_serializer_context(self): # Override this method to add more stuff # to the serializer context return { 'request': self.request, 'format': self.format_kwarg, 'view': self } @laceynwilliams | @revsys
27. When to override get_serializer_context(): When you need to add something to the context so your serializer can use it @laceynwilliams | @revsys
28. In your methods, you can run: serializer = self.get_serializer() instead of accessing your serializer directly. @laceynwilliams | @revsys
29. Methods that come with the mixins for ModelViewSet @laceynwilliams | @revsys
30. @laceynwilliams | @revsys
31. class CreateModelMixin: def create(self, request, *args, **kwargs): serializer = self.get_serializer(data=request.data) serializer.is_valid(raise_exception=True) self.perform_create(serializer) headers = self.get_success_headers(serializer.data) return Response( serializer.data, status=status.HTTP_201_CREATED, headers=headers ) @laceynwilliams | @revsys
32. class CreateModelMixin: def create(self, request, *args, **kwargs): serializer = self.get_serializer(data=request.data) serializer.is_valid(raise_exception=True) self.perform_create(serializer) headers = self.get_success_headers(serializer.data) return Response( serializer.data, status=status.HTTP_201_CREATED, headers=headers ) @laceynwilliams | @revsys
33. class CreateModelMixin: def create(self, request, *args, **kwargs): serializer = self.get_serializer(data=request.data) serializer.is_valid(raise_exception=True) self.perform_create(serializer) headers = self.get_success_headers(serializer.data) return Response( serializer.data, status=status.HTTP_201_CREATED, headers=headers ) @laceynwilliams | @revsys
34. class CreateModelMixin: def perform_create(self, serializer): serializer.save() @laceynwilliams | @revsys
35. class CreateModelMixin: def create(self, request, *args, **kwargs): serializer = self.get_serializer(data=request.data) serializer.is_valid(raise_exception=True) self.perform_create(serializer) headers = self.get_success_headers(serializer.data) return Response( serializer.data, status=status.HTTP_201_CREATED, headers=headers ) @laceynwilliams | @revsys
36. ... Why did you show me a bunch of source code? @laceynwilliams | @revsys
37. "I want my books to have a lot of data for the detail endpoints, but only some of the data for the list endpoint. Can I do that?" @laceynwilliams | @revsys
38. from rest_framework.permissions import AllowAny from rest_framework.viewsets import ModelViewSet from .models import Book from .serializers import BookDetailSerializer, BookListSerializer class BookViewSet(ModelViewSet): queryset = Book.objects.all() serializer_class = BookDetailSerializer permission_classes = [AllowAny] def get_serializer_class(self): if self.action in ["list"]: return BookListSerializer return super().get_serializer_class() @laceynwilliams | @revsys
39. "A#er I create a book, I want to use a different, more detailed serializer to return it." @laceynwilliams | @revsys
40. Reminder class CreateModelMixin: def create(self, request, *args, **kwargs): serializer = self.get_serializer(data=request.data) serializer.is_valid(raise_exception=True) self.perform_create(serializer) headers = self.get_success_headers(serializer.data) return Response( serializer.data, status=status.HTTP_201_CREATED, headers=headers ) @laceynwilliams | @revsys
41. Reminder class CreateModelMixin: def create(self, request, *args, **kwargs): serializer = self.get_serializer(data=request.data) serializer.is_valid(raise_exception=True) self.perform_create(serializer) headers = self.get_success_headers(serializer.data) return Response( serializer.data, status=status.HTTP_201_CREATED, headers=headers ) @laceynwilliams | @revsys
42. from rest_framework.permissions import AllowAny from rest_framework.viewsets import ModelViewSet from .models import Book from .serializers import BookSerializer, BookCreatedSerializer class BookViewSet(ModelViewSet): ... def create(self, request, *args, **kwargs): serializer = self.get_serializer(data=request.data) serializer.is_valid(raise_exception=True) # self.perform_create(serializer) instance = serializer.save() return_serializer = BookCreatedSerializer(instance) headers = self.get_success_headers(return_serializer.data) return Response( return_serializer.data, status=status.HTTP_201_CREATED, headers=headers ) @laceynwilliams | @revsys
43. from rest_framework.permissions import AllowAny from rest_framework.viewsets import ModelViewSet from .models import Book from .serializers import BookSerializer, BookCreatedSerializer class BookViewSet(ModelViewSet): ... def create(self, request, *args, **kwargs): serializer = self.get_serializer(data=request.data) serializer.is_valid(raise_exception=True) # self.perform_create(serializer) instance = serializer.save() return_serializer = BookCreatedSerializer(instance) headers = self.get_success_headers(return_serializer.data) return Response( return_serializer.data, status=status.HTTP_201_CREATED, headers=headers ) @laceynwilliams | @revsys
44. from rest_framework.permissions import AllowAny from rest_framework.viewsets import ModelViewSet from .models import Book from .serializers import BookSerializer, BookCreatedSerializer class BookViewSet(ModelViewSet): ... def create(self, request, *args, **kwargs): serializer = self.get_serializer(data=request.data) serializer.is_valid(raise_exception=True) # self.perform_create(serializer) instance = serializer.save() return_serializer = BookCreatedSerializer(instance) headers = self.get_success_headers(return_serializer.data) return Response( return_serializer.data, status=status.HTTP_201_CREATED, headers=headers ) @laceynwilliams | @revsys
45. "But I don't need ALL those endpoints. Only most of them." @laceynwilliams | @revsys
46. Do everything except delete from rest_framework.generics import GenericAPIView from rest_framework.mixins import CreateModelMixin, RetrieveModelMixin, UpdateModelMixin, ListModelMixin # import models and serializers... class BookViewSet( CreateModelMixin, RetrieveModelMixin, UpdateModelMixin, ListModelMixin, GenericAPIView ): ... @laceynwilliams | @revsys
47. DRF mixes and matches for you ✓ UpdateAPIView = UpdateModelMixin + GenericAPIView ✓ CreateAPIView ✓ ListAPIView ✓ RetrieveAPIView ✓ DestroyAPIView ✓ ReadOnlyModelViewSet ✓ RetrieveDestroyAPIView ✓ RetrieveUpdateDestroy APIView ✓ ListCreateAPIView ✓ RetrieveUpdateAPIView @laceynwilliams | @revsys
48. "Can we have an endpoint that just shows our featured books?" @laceynwilliams | @revsys
49. from rest_framework.decorators import action class BookViewSet(ModelViewSet): queryset = Book.objects.all() serializer_class = BookDetailSerializer def get_serializer_class(self): if self.action in ["list", "featured"]: return BookListSerializer return super().get_serializer_class() @action(detail=False, methods=["get"]) def featured(self, request): books = self.get_queryset().filter(featured=True) serializer = self.get_serializer(books, many=True) return Response(serializer.data, status=status.HTTP_200_OK) @laceynwilliams | @revsys
50. from rest_framework.decorators import action class BookViewSet(ModelViewSet): queryset = Book.objects.all() serializer_class = BookDetailSerializer def get_serializer_class(self): if self.action in ["list", "featured"]: return BookListSerializer return super().get_serializer_class() @action(detail=False, methods=["get"]) def featured(self, request): books = self.get_queryset().filter(featured=True) serializer = self.get_serializer(books, many=True) return Response(serializer.data, status=status.HTTP_200_OK) @laceynwilliams | @revsys
51. url = GET /books/featured/ @laceynwilliams | @revsys
52. from rest_framework.decorators import action class BookViewSet(ModelViewSet): queryset = Book.objects.all() serializer_class = BookDetailSerializer def get_serializer_class(self): if self.action in ["list", "featured"]: return BookListSerializer return super().get_serializer_class() @action(detail=False, methods=["get"]) def featured(self, request): books = self.get_queryset().filter(featured=True) serializer = self.get_serializer(books, many=True) return Response(serializer.data, status=status.HTTP_200_OK) @laceynwilliams | @revsys
53. from rest_framework.decorators import action class BookViewSet(ModelViewSet): queryset = Book.objects.all() serializer_class = BookDetailerializer def get_serializer_class(self): if self.action in ["list", "featured"]: return BookListSerializer return super().get_serializer_class() @action(detail=False, methods=["get"]) def featured(self, request): books = self.get_queryset().filter(featured=True) serializer = self.get_serializer(books, many=True) return Response(serializer.data, status=status.HTTP_200_OK) @laceynwilliams | @revsys
54. from rest_framework.decorators import action class BookViewSet(ModelViewSet): queryset = Book.objects.all() serializer_class = BookDetailerializer def get_serializer_class(self): if self.action in ["list", "featured"]: return BookListSerializer return super().get_serializer_class() @action(detail=False, methods=["get"]) def featured(self, request): books = self.get_queryset().filter(featured=True) serializer = self.get_serializer(books, many=True) return Response(serializer.data, status=status.HTTP_200_OK) @laceynwilliams | @revsys
55. Thank you! To Tom Chris*e and the maintainers of DRF. To Vinta So*ware and the maintainers of Classy DRF. To Beki Post and Jeff Triple3 for their help with this talk. To Vancouver PyLadies for le4ng me preview this talk with you. To PyCascades! @laceynwilliams | @revsys
56. ✉ lacey@revsys.com " @laceynwilliams # laceyhenschel.com # revsys.com @laceynwilliams | @revsys