Python and django, how to extract data from the queryset

Question

I have a question for you. I have the following class:

class StatoPatrimoniale(models.Model):
    reference_date=models.DateField()
    income=models.DecimalField()
    debt=models.DecimalField()

After that I have named a new variable last_account_year in th following manner:

now=datetime.datetime.now()
last_account_year=float(now.year)-1

Now I want to create a function that give me the possibility to extract the income and debt objects filtering them using the last_account_year and the year in the reference_date . How could I get this result?

Answer 1

You should use the model date field lookup :

StatoPatrimoniale.objects.filter(reference_date__year=last_account_year)

And in a function encapsulating the logic and fixing it to zero if it doesn't exists:

def func(year):
    queryset = StatoPatrimoniale.objects.filter(reference_date__year=year)
    return queryset if queryset.exists() else 0

Answer 2

You can use.filter() to filter your query and values_list() to get values: here is an exemple:

StatoPatrimoniale.objects.filter(reference_date__year=last_account_year).values_list('income', 'debt')