How to return generated file download with Django REST Framework?

Question

I need to return generated file download as a Django REST Framework response. I tried the following:

def retrieve(self, request, *args, **kwargs):
    template = webodt.ODFTemplate('test.odt')
    queryset = Pupils.objects.get(id=kwargs['pk'])
    serializer = StudentSerializer(queryset)
    context = dict(serializer.data)
    document = template.render(Context(context))
    doc = converter().convert(document, format='doc')
    res = HttpResponse(
        FileWrapper(doc),
        content_type='application/msword'
    )
    res['Content-Disposition'] = u'attachment; filename="%s_%s.zip"' % (context[u'surname'], context[u'name'])
    return res

But it returns a msword document as json.

How do I make it start downloading as file instead?

Answer 1

Here's an example of returning a file download directly from DRF. The trick is to use a custom renderer so you can return a Response directly from the view:

from django.http import FileResponse
from rest_framework import viewsets, renderers
from rest_framework.decorators import action

class PassthroughRenderer(renderers.BaseRenderer):
    """
        Return data as-is. View should supply a Response.
    """
    media_type = ''
    format = ''
    def render(self, data, accepted_media_type=None, renderer_context=None):
        return data

class ExampleViewSet(viewsets.ReadOnlyModelViewSet):
    queryset = Example.objects.all()

    @action(methods=['get'], detail=True, renderer_classes=(PassthroughRenderer,))
    def download(self, *args, **kwargs):
        instance = self.get_object()

        # get an open file handle (I'm just using a file attached to the model for this example):
        file_handle = instance.file.open()

        # send file
        response = FileResponse(file_handle, content_type='whatever')
        response['Content-Length'] = instance.file.size
        response['Content-Disposition'] = 'attachment; filename="%s"' % instance.file.name

        return response

Note I'm using a custom endpoint download instead of the default endpoint retrieve, because that makes it easy to override the renderer just for this endpoint instead of for the whole viewset -- and it tends to make sense for list and detail to return regular JSON anyway. If you wanted to selectively return a file download you could add more logic to the custom renderer.