AttributeError 'list' object has no attribute 'get'

Question

When querying my API with format=json I get the following error:

AttributeError 'list' object has no attribute 'get'

Interestingly enough it doesn't happen with the Django Rest Framework API UI. Only when format=json.

Here is my list method:

def list(self, request):
    queryset = dataset_models.DataSet.objects.all()
    serializer = serializers.DataSetListSerializer(queryset, many=True)
    return Response(serializer.data)

And my serializer:

class DataSetListSerializer(serializers.ModelSerializer):
    class Meta:
        model = dataset_models.DataSet

Traceback:

Traceback:
File "/usr/lib/python2.7/site-packages/Django-1.5.7.example1-py2.7.egg/django/core/handlers/base.py" in get_response
  187.                 response = middleware_method(request, response)

Exception Type: AttributeError at /api/v0/a-cb4be7e8/p/example.com/dataset/
Exception Value: 'list' object has no attribute 'get'

What gives?

Solution

When you use many=True it serializes several objects and puts them in a list. As the JSONResponse class expects to be passed a dict (unless also passed safe=False), I'm guessing your Response class does as well.

Comments

[hanleyhansen]

I took another look at the Response class. It's just a subclass of SimpleTemplateResponse. However, I did notice in the documentation that the content_type parameter is supposed to be set automatically if properly determined by content negotiation. In other words, something in the content negotiation seems to be off because if i pass the content_type it works.

[Denis Cornehl]

As I recall you can perfectly pass lists to the response-class in DRF.

[Ross Ridge]

It does seem you're supposed to be able to. A simple way to test whether the list being passed to Response is the list being complained about in the exception would be to make it a dict and see what happens. Eg. Response(dict(enumerate(serializer.data)))

[hanleyhansen]

@RossRidge Passing a dict works fine. Something like Response({'data': serializer.data}).

[Ross Ridge]

Have you had any luck trying to get a full traceback? Done the obvious like set DEBUG=True in you Django settings? I think we'll need the full traceback to figure out why it doesn't work with lists.

[hanleyhansen]

@RossRidge I did paste the full traceback above and debug is set to True. The message is not all that useful.