How to use the djangorestframework.status.HTTP_404_NOT_FOUND function in djangorestframework

"""
        3. def for post Diem danh to server:
          post:
          "classId": "xxx"
          "date":"20-04-2012"
          "list":"studentId-status-20-04-2012%studentId-status-20-04-2012%studentId-status-20-04-2012"

        status la trang thai di hoc: K-Nghi ko phep; P- Nghi co phep; M-Di muon;
        """
        class_id = request.POST['classId']
        day = request.POST['date']
        data = request.POST['list']
        try:
            _class = Class.objects.get(id = int(class_id))
        except ObjectDoesNotExist:
            return Response(status.HTTP_404_NOT_FOUND)
        if (is_teacher(request)
                and request.user.teacher in _class.associated_teacher()):
            date_parts = day.split('-')
            try:
                response = dd(request,
                            class_id,
                            date_parts[0],
                            date_parts[1],
                            date_parts[2],
                            api_called=True,
                            data=data)
                if response.status_code == 200:
                    return Response(status.HTTP_200_OK)
                else:
                    return Response(status.HTTP_400_BAD_REQUEST)
            except Exception as e:

def delete(self, request, *args, **kwargs):
        model = self.resource.model

        try:
            if args:
                # If we have any none kwargs then assume the last represents the primrary key
                instance = model.objects.get(pk=args[-1], **kwargs)
            else:
                # Otherwise assume the kwargs uniquely identify the model
                instance = model.objects.get(**kwargs)
        except model.DoesNotExist:
            raise ErrorResponse(status.HTTP_404_NOT_FOUND, None, {})

        instance.delete()
        return

def delete(self, request, *args, **kwargs):
        try:
            if args:
                # If we have any none kwargs then assume the last represents the primrary key
                instance = self.model.objects.get(pk=args[-1], **kwargs)
            else:
                # Otherwise assume the kwargs uniquely identify the model
                instance = self.model.objects.get(**kwargs)
        except self.model.DoesNotExist:
            raise ErrorResponse(status.HTTP_404_NOT_FOUND, None, {})

        instance.delete()
        return

def handle_exception(self, exc):
        """
        Handle any exception that occurs, by returning an appropriate response,
        or re-raising the error.
        """
        if isinstance(exc, exceptions.Throttled):
            self.headers['X-Throttle-Wait-Seconds'] = '%d' % exc.wait

        if isinstance(exc, exceptions.APIException):
            return Response({'detail': exc.detail}, status=exc.status_code)
        elif isinstance(exc, Http404):
            return Response({'detail': 'Not found'},
                            status=status.HTTP_404_NOT_FOUND)
        elif isinstance(exc, PermissionDenied):
            return Response({'detail': 'Permission denied'},
                            status=status.HTTP_403_FORBIDDEN)
        raise

    @need_login
    @school_function
    def get(self, request, class_id):
        try:
            cl = Class.objects.get(id=class_id)
        except ObjectDoesNotExist:
            return Response(status=status.HTTP_404_NOT_FOUND)
        subjects = cl.subject_set.all()
        result = []
        for s in subjects:
            result.append({
                'name': s.name,
                'type': s.type,
                'hs': s.hs,
                'nx': s.nx,
                'primary': s.primary,
                'index': s.index,
                'number_lession': s.number_lession,
                'teacher': s.teacher_id.full_name()})
        return Response(status=status.HTTP_200_OK, content=result)

def _get_instance_or_404(self, *args, **kwargs):
        from djangorestframework.response import ErrorResponse
        from djangorestframework import status

        model = self.resource.model
        query_kwargs = self.get_query_kwargs(self.request, *args, **kwargs)
        try:
            return self.get_instance(**query_kwargs)
        except model.DoesNotExist:
            raise ErrorResponse(status.HTTP_404_NOT_FOUND, None, {})

def get(self, request, *args, **kwargs):
        try:
            if args:
                # If we have any none kwargs then assume the last represents the primrary key
                instance = self.model.objects.get(pk=args[-1], **kwargs)
            else:
                # Otherwise assume the kwargs uniquely identify the model
                instance = self.model.objects.get(**kwargs)
        except self.model.DoesNotExist:
            raise ErrorResponse(status.HTTP_404_NOT_FOUND)

        return instance

def delete(self, request, key):
        """
        Delete a stored object, by removing it's pickled file.
        """
        filename = get_filename(key)
        if not os.path.exists(filename):
            return Response(status.HTTP_404_NOT_FOUND)
        os.remove(filename)

def get(self, request, num):
        """
        Handle GET requests.
        Returns a simple string indicating which view the GET request was for.
        """
        if int(num) > 2:
            return Response(status.HTTP_404_NOT_FOUND)
        return "GET request to AnotherExampleResource %s" % num

def delete(self, request, *args, **kwargs):
        """
        Only the creator should be able to delete an instance.
        """
        model = self.resource.model
        query_kwargs = self.get_query_kwargs(request, *args, **kwargs)

        try:
            instance = self.get_instance(**query_kwargs)
        except model.DoesNotExist:
            raise ErrorResponse(status.HTTP_404_NOT_FOUND, None, {})

        if instance.created_by == self.user:
            instance.delete()
        else:
            raise ErrorResponse(status.HTTP_401_UNAUTHORIZED, None, {})