I am attempting to create a semi-dynamic aggregate function that will return the sums of all fields within a list. The assumption is that running get_query_set() will return a filtered query that contains all the fields in the list and some others that may not play so well with a Sum aggregate (date fields, char fields, Foreign Keys, etc...)

Best examples I've come up with so far are below, this is largely a python question with Django specific usage though my Python-Fu is not the strongest yet...

Works

qs = cl.get_query_set().aggregate(Sum('permits_submitted'), Sum('permits_pulled'), Sum('permits_posted'))

return: {'permits_pulled__sum': 5772, 'permits_posted__sum': 6723, 'permits_submitted__sum': 7276}

Does not work

qs = cl.get_query_set().aggregate(Sum('permits_submitted')).aggregate(Sum('permits_pulled'))

return: error

qs = cl.get_query_set().aggregate(Sum('permits_submitted', 'permits_pulled', Sum('permits_posted'))

return: error

Does not work - presents the idea

tuple = (
        'permits_submitted',
        'permits_pulled',
        'permits_posted',
    )

qs = cl.get_query_set()
for field in tuple:
    qs.aggregate(Sum(field))

r开发者_StackOverflow中文版eturn: error

qs = cl.get_query_set()
qs.aggregate(*[Sum(field) for field in tuple])

return:

[<permit_runner: User's report for 2010-02-18>, <permit_runner: User's report for 2010-02-19>, '...(remaining elements truncated)...'] 

(this is the same as the return without aggregation)

WORKS

qs = cl.get_query_set()
qs = qs.aggregate(*[Sum(field) for field in tuple])

had missed defining qs = when adding the aggregation - helps to take a break for a few minutes and look fresh

Since this work, I put that as an answer, so people will find it easily when googling:

qs = cl.get_query_set()
qs = qs.aggregate(*[Sum(field) for field in tuple])

Creating dynamic aggregations (or dynamic annotations)

from typing import Dict
from django.db.models import Q, Sum


# 1. Prepare your querysets
years = year_allowances.values_list("year", flat=True)  
time_aways = TimeAway.objects.filter(  
    sequence__pk__in=sequences.values_list("pk", flat=True)  
).actual_paid_sick_leave()  

# 2. Define your individual aggregate expression.
def get_aggregate(key) -> Dict[str, Sum]:  
    return {  
        str(key): Sum(F('actual_paid_sick_leave'), filter=Q(local_timezone_start__year=key))  
    }  

# 3. Create the dictionary of aggregate expressions.
aggregate_expressions = {}  
ds = [{**get_aggregate(year)} for year in years]  
for d in ds:  
    aggregate_expressions.update(d)

# 4. Create your aggregations.
x = time_aways.aggregate(**aggregate_expressions)
>> x = {'2021': datetime.timedelta(0), '2022': datetime.timedelta(days=5)}