# models.py
class Data:
    def __init__(self, data_from_file):
        self.data_from_file = data_from_file

# serializers.py
class DataSerializer(serializers.Serializer):
    data_from_file = serializers.CharField()

# views.py
class DataView(ListAPIView):
    serializer_class = DataSerializer

    def get_queryset(self):
        mult = self.request.query_params.get('mult', None)
        y = np.loadtxt('media/data_vv.txt')[:10]

        if mult is not None:
            y *= float(mult)

        y = list(y)
        x = list(range(len(y)))
        data = {'x': x, 'y': y}

        data = Data(json.dumps(data))
        serializer = DataSerializer(data)

        return JsonResponse(serializer.data, safe=False)

[16/Jul/2019 21:49:31] "GET /data?mult=2.5 HTTP/1.1" 301 0
Internal Server Error: /data/
Traceback (most recent call last):
  File "C:\Users\Przemo\Documents\venv\lib\site-packages\rest_framework\fields.py", line 443, in get_attribute
    return get_attribute(instance, self.source_attrs)
  File "C:\Users\Przemo\Documents\venv\lib\site-packages\rest_framework\fields.py", line 93, in get_attribute
    instance = getattr(instance, attr)
AttributeError: 'bytes' object has no attribute 'data_from_file'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\Users\Przemo\Documents\venv\lib\site-packages\django\core\handlers\exception.py", line 34, in inner
    response = get_response(request)
  File "C:\Users\Przemo\Documents\venv\lib\site-packages\django\core\handlers\base.py", line 115, in _get_response

    response = self.process_exception_by_middleware(e, request)
  File "C:\Users\Przemo\Documents\venv\lib\site-packages\django\core\handlers\base.py", line 113, in _get_response

    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "C:\Users\Przemo\Documents\venv\lib\site-packages\django\views\decorators\csrf.py", line 54, in wrapped_vie
w
    return view_func(*args, **kwargs)
  File "C:\Users\Przemo\Documents\venv\lib\site-packages\django\views\generic\base.py", line 71, in view
    return self.dispatch(request, *args, **kwargs)
  File "C:\Users\Przemo\Documents\venv\lib\site-packages\rest_framework\views.py", line 497, in dispatch
    response = self.handle_exception(exc)
  File "C:\Users\Przemo\Documents\venv\lib\site-packages\rest_framework\views.py", line 457, in handle_exception
    self.raise_uncaught_exception(exc)
  File "C:\Users\Przemo\Documents\venv\lib\site-packages\rest_framework\views.py", line 468, in raise_uncaught_exc
eption
    raise exc
  File "C:\Users\Przemo\Documents\venv\lib\site-packages\rest_framework\views.py", line 494, in dispatch
    response = handler(request, *args, **kwargs)
  File "C:\Users\Przemo\Documents\venv\lib\site-packages\rest_framework\generics.py", line 199, in get
    return self.list(request, *args, **kwargs)
  File "C:\Users\Przemo\Documents\venv\lib\site-packages\rest_framework\mixins.py", line 46, in list
    return Response(serializer.data)
  File "C:\Users\Przemo\Documents\venv\lib\site-packages\rest_framework\serializers.py", line 757, in data
    ret = super().data
  File "C:\Users\Przemo\Documents\venv\lib\site-packages\rest_framework\serializers.py", line 261, in data
    self._data = self.to_representation(self.instance)
  File "C:\Users\Przemo\Documents\venv\lib\site-packages\rest_framework\serializers.py", line 675, in to_represent
ation
    self.child.to_representation(item) for item in iterable
  File "C:\Users\Przemo\Documents\venv\lib\site-packages\rest_framework\serializers.py", line 675, in <listcomp>
    self.child.to_representation(item) for item in iterable
  File "C:\Users\Przemo\Documents\venv\lib\site-packages\rest_framework\serializers.py", line 513, in to_represent
ation
    attribute = field.get_attribute(instance)
  File "C:\Users\Przemo\Documents\venv\lib\site-packages\rest_framework\fields.py", line 476, in get_attribute
    raise type(exc)(msg)
AttributeError: Got AttributeError when attempting to get a value for field `data_from_file` on serializer `DataSe
rializer`.
The serializer field might be named incorrectly and not match any attribute or key on the `bytes` instance.
Original exception text was: 'bytes' object has no attribute 'data_from_file'.
[16/Jul/2019 21:49:31] "GET /data/?mult=2.5 HTTP/1.1" 500 18928