What is the "format" parameter used for in Django REST Framework views?

Question

In the DRF documentation example found here:

class SnippetList(APIView):
    """
    List all snippets, or create a new snippet.
    """
    def get(self, request, format=None):
        snippets = Snippet.objects.all()
        serializer = SnippetSerializer(snippets, many=True)
        return Response(serializer.data)

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

The above sample has an unused format parameter in both the get() and post() methods. I have stepped through the rest_framework source and I cannot find any instance where this parameter is handed off to the get() or post() method by the dispatcher. Is this parameter required to be present in the method definition? If so, what is it used for? When is it used?

Answer 1

I found that the format parameter is used when you use format suffixes. So now I wanted to find out how this was used because nothing in the handler code seems to be using it but somehow it still works (magic behavior).

I went ahead and used pdb to trace execution of the view and found that APIView.initial() extracts this parameter from the kwargs and the uses it in the call to APIView.perform_content_negotiation() which selects the renderer and media type to use in the response.

Answer 2

Basiclly this "format" parameter is used to define the output response format, like: csv, json, etc