How to display all dates for multiple model annotations in django - django

Question

So I'm working on a website, and I want to have some kind of a summary page to display the data that I have. Let's say I have these models:
class IceCream(TimeStampedModel):
name = models.CharField()
color = models.CharField()
class Cupcake(TimeStampedModel):
name = models.CharField()
icing = models.CharField()
So on this page, users will be able to input a date range for the summary. I'm using DRF to serialize the data and to display them on the view actions. After I receive the filter dates, I will filter out the IceCream objects and Cupcake objects using the created field from TimeStampedModel.
#action(detail=False, methods=['get'])
def dessert_summary(self, request, **kwargs):
start_date = self.request.query_params.get('start_date')
end_date = self.request.query_params.get('end_date')
cupcakes = Cupcake.objects.filter(created__date__range=[start_date, end_date])
ice_creams = IceCream.objects.filter(created__date__range=[start_date, end_date])
After filtering, I want to count the total cupcakes and the total ice creams that is created within that period of time. But I also want to group them by the dates, and display the total count for both ice creams and cupcakes based on that date. So I tried to annotate the querysets like this:
cupcakes = cupcakes.annotate(date=TruncDate('created'))
cupcakes = cupcakes.values('date')
cupcakes = cupcakes.annotate(total_cupcakes=Count('id'))
ice_creams = ice_creams.annotate(date=TruncDate('created'))
ice_creams = ice_creams.values('date')
ice_creams = ice_creams.annotate(total_ice_creams=Count('id'))
So I want the result to be something like this:
{
'summary': [{
'date': "2020-09-24",
'total_ice_creams': 10,
'total_cupcakes': 7,
'total_dessert': 17
}, {
'date': "2020-09-25',
'total_ice_creams': 6,
'total_cupcakes': 5,
'total_dessert': 11
}]
}
But right now this is what I am getting:
{
'summary': [{
'cupcakes': [{
'date': "2020-09-24",
'total_cupcakes': 10,
}, {
'date': "2020-09-25",
'total_cupcakes': 5,
}],
'ice_creams': [{
'date': "2020-09-24",
'total_ice_creams': 7,
}, {
'date': "2020-09-27",
'total_ice_creams': 6,
}]
}]
}
What I want to ask is how do I get all the dates of both querysets, sum the ice creams and cupcakes, and return the data like the expected result? Thanks in advance for your help!

Answer 1

So here's what you can do:
gather all icecream/cupcakes count data into a dictionary
icecream_dict = {obj['date']: obj['count'] for obj in ice_creams}
cupcakes_dict = {obj['date']: obj['count'] for obj in cupcakes}
create a sorted list with all the dates
all_dates = sorted(set(list(icecream_dict.keys()) + list(cupcakes_dict.keys())))
create a list with items for each date and their count
result = []
for each_date in all_dates:
total_ice_creams = icecream_dict.get(each_date, 0)
total_cupcakes = cupcakes_dict.get(each_date, 0)
res = {
'date': each_date,
'total_ice_creams': total_ice_creams,
'total_cupcakes': total_cupcakes,
'total_dessert': total_ice_creams + total_cupcakes
}
result.append(res)
# check the result
print(result)
Hint: If you plan to add more desert-like models, consider have a base model Desert that you could query directly instead of querying each desert type model.