PUT-as-create mixin class for Django REST framework.

put_as_create.py

class AllowPUTAsCreateMixin(object):
    """
    The following mixin class may be used in order to support PUT-as-create
    behavior for incoming requests.
    """
    def update(self, request, *args, **kwargs):
        partial = kwargs.pop('partial', False)
        instance = self.get_object_or_none()
        serializer = self.get_serializer(instance, data=request.data, partial=partial)
        serializer.is_valid(raise_exception=True)

        if instance is None:
            lookup_url_kwarg = self.lookup_url_kwarg or self.lookup_field
            lookup_value = self.kwargs[lookup_url_kwarg]
            extra_kwargs = {self.lookup_field: lookup_value}
            serializer.save(**extra_kwargs)
            return Response(serializer.data, status=status.HTTP_201_CREATED)

        serializer.save()
        return Response(serializer.data)

    def partial_update(self, request, *args, **kwargs):
        kwargs['partial'] = True
        return self.update(request, *args, **kwargs)

    def get_object_or_none(self):
        try:
            return self.get_object()
        except Http404:
            if self.request.method == 'PUT':
                # For PUT-as-create operation, we need to ensure that we have
                # relevant permissions, as if this was a POST request.  This
                # will either raise a PermissionDenied exception, or simply
                # return None.
                self.check_permissions(clone_request(self.request, 'POST'))
            else:
                # PATCH requests where the object does not exist should still
                # return a 404 response.
                raise
 

This seems to work for me with Django 4.2 and Python 3.11. Although I haven't tested it with permissions.

from django.http
import rest_framework.mixins

class AllowPUTAsCreateMixin(rest_framework.mixins.CreateModelMixin, rest_framework.mixins.UpdateModelMixin):

    def put(self, request, *args, **kwargs):
        try:
            return self.update(request, *args, **kwargs)
        except Http404:
            pass
        return self.create(request, *args, **kwargs)

With this I can create a view that allows retrieving via GET and upsert via PUT.

import rest_framework.generics
import rest_framework.serializers

class Serializer(rest_framework.serializers.ModelSerializer):
    ...  # TODO: As normal

class RetrieveCreatePatch(AllowPUTAsCreateMixin, rest_framework.generics.RetrieveAPIView):
    queryset = MyModel.objects.all()
    serializer_class = Serializer