Django Rest Framework: changing output format of annotated field in queryset

Question

Hello StackOverflow community,

I am currently struggling with specifying an output format in my views.py. I have a column "date" which is using following format: 2021-01-14. In my response, I would like to change the date format so that it only shows the year 2021.

I already tried it with Cast but it seems like this is not the right approach. For this view, I do not use a Serializer, hence adding it there would not be an option.

views.py

class FilterParams(generics.ListAPIView):
    model = Variants
    queryset = Variants.objects.all()
    def get(self, request, *args, **kwargs):
        queryset = self.get_queryset()
        ModelsByYears = queryset.values('model').distinct().annotate(min_year=Min('date')).annotate(max_year=Max('date')).order_by('model')
        return Response(data= {'ModelsByYears':ModelsByYears})

What I tried:

class FilterParams(generics.ListAPIView):
    model = Variants
    queryset = Variants.objects.all()
    def get(self, request, *args, **kwargs):
        queryset = self.get_queryset()
        ModelsByYears = queryset.values('model').distinct().annotate(min_year=Min(Cast('date', DateTimeField(format="%Y")))).annotate(max_year=Max('date')).order_by('model')
        return Response(data= {'ModelsByYears':ModelsByYears})

Error message

TypeError: __init__() got an unexpected keyword argument 'format'

iklinac · Accepted Answer · 2021-01-18 20:52:48Z

1

You should use Extract/ExtractYear database function instead

Takes an expression representing a DateField, DateTimeField, TimeField, or DurationField and a lookup_name, and returns the part of the date referenced by lookup_name as an IntegerField. Django usually uses the databases’ extract function, so you may use any lookup_name that your database supports.

answered Jan 18, 2021 at 20:52

iklinac

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1 Comment

DevDjas Over a year ago

Works great with Extract. Thank you very much for your help :)

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