#view.py:
class AllData(viewsets.ModelViewSet):
    queryset = Run.objects.all()
    serializer_class = RunSerializer

    def get_queryset(self):
        queryset = self.queryset
        start_date = self.request.query_params.get('start_date')
        end_date = self.request.query_params.get('end_date')
        if start_date is not None and end_date is not None:
            queryset = queryset.filter(Q(date__gte=start_date) & Q(date__lte=end_date))
        return queryset


#serializers.py:
class RunSerializer(serializers.ModelSerializer):
    class Meta:
        model = Run
        fields = '__all__'


#models.py:
class Run(models.Model):
    date = models.DateField()
    distance = models.DecimalField(max_digits=5, decimal_places=3)
    time = models.SmallIntegerField()

    def __str__(self):
        return str(self.distance)


#urls.py:
router = DefaultRouter()
router.register('all_runs', AllData, basename='all_runs')

urlpatterns = [
    path('average_data/', AverageData.as_view(), name='average_data'),
]

urlpatterns += router.urls