Django REST Framework - return a value from get_queryset?

Question

I am trying to return a value from get_queryset .

def get_queryset(self):
   if self.request.user.is_superuser:
        return StockPriceModel.objects.order_by('ticker').distinct()
   elif not self.request.user.is_authenticated:
        print('in')
        print(self.request.data)
        last_price = StockPriceModel.objects.all().filter(
                ticker=self.request.data['ticker']).order_by('-last_date_time')[0].last_price
        print(last_price)
        return last_price

last price gets printed without an issue.

In return I get various errors:

TypeError at /api/stock-prices-upload/ 'float' object is not iterable

If I try to return till:

StockPriceModel.objects.all().filter(
                ticker=self.request.data['ticker']).order_by('-last_date_time')

It works.

As soon as I try to return just the 0 position queryset I get errors.

I assume this is because get_queryset is supposed to return a queryset . Not sure how to return just the value.

Edit:

I am now trying to get only the latest row ie [0] form the data but still getting the same errors ie

StockPriceModel object is not iterable

# The current output if I don't add the [0] i.e. try to get the last row of data

[{"id":23,"last_price":"395.2","name":null,"country":null,"sector":null,"industry":null,"ticker":"HINDALCO","high_price":null,"last_date_time":"2022-10-20T15:58:26+04:00","created_at":"2022-10-20T23:20:37.499166+04:00"},{"id":1717,"last_price":"437.5","name":null,"country":null,"sector":null,"industry":null,"ticker":"HINDALCO","high_price":438.9,"last_date_time":"2022-11-07T15:53:41+04:00","created_at":"2022-11-07T14:26:40.763060+04:00"}]

Expected response:

[{"id":1717,"last_price":"437.5","name":null,"country":null,"sector":null,"industry":null,"ticker":"HINDALCO","high_price":438.9,"last_date_time":"2022-11-07T15:53:41+04:00","created_at":"2022-11-07T14:26:40.763060+04:00"}]

I have tried using last , get etc. Just won't work.

Answer 1

Because, get_queryset() always return a queryset of objects or a list of objects.

You cannot return an object or a field from the get_queryset method.

the last_price value will be printed, but it is a field value and therefore the get_queryset method will not return it.

When you add [0] , it takes the first object from the filtered queryset. Till that point, it is a queryset of objects.

Answer 2

This is a bit hacky, and I am sure there must be a better way to do this.

I wanted to get return of either a single row (last_date_time) based or the last_price value.

I wrapped the query:

# removed the .last_price
last_price = StockPriceModel.objects.all().filter(
                ticker=self.request.data['ticker']).order_by('-last_date_time')[0]
last_price = [last_price] # made it into a list, i.e. iterable
return last_price

And now I can get the last row.