[Django]-Django: Calculate the Sum of the column values through query

Use .aggregate(Sum('column'))['column__sum'] reefer my example below

sum = Sale.objects.filter(type='Flour').aggregate(Sum('column'))['column__sum']

Annotate adds a field to results:

>> Order.objects.annotate(total_price=Sum('price'))
<QuerySet [<Order: L-555>, <Order: L-222>]>

>> orders.first().total_price
Decimal('340.00')

Aggregate returns a dict with asked result:

>> Order.objects.aggregate(total_price=Sum('price'))
{'total_price': Decimal('1260.00')}

Using cProfile profiler, I find that in my development environment, it is more efficient (faster) to sum the values of a list than to aggregate using Sum().
eg:

sum_a = sum([item.column for item in queryset]) # Definitely takes more memory.
sum_b = queryset.aggregate(Sum('column')).get('column__sum') # Takes about 20% more time.

I tested this in different contexts and it seems like using aggregate takes always longer to produce the same result. Although I suspect there might be advantages memory-wise to use it instead of summing a list.

Previous answers are pretty well, also, you may get that total with a line of vanilla code…

items = ItemPrice.objects.all()
total_price = sum(items.values_list('price', flat=True))

You could also get the sum this way:

def total_sale(self):
    total = Sale.objects.aggregate(TOTAL = Sum('amount'))['TOTAL']
    return total

Replace the ‘amount’ with the column name from your model you want to calculate the sum of and replace ‘Sale’ with your model name.

You need to use aggregate() and Sum() to calculate the sum of price column as shown below. *The query with all() is equivalent to the query without all() as shown below:

from django.db.models import Sum

print(ItemPrice.objects.all().aggregate(Sum('price')))
print(ItemPrice.objects.aggregate(Sum('price')))

Then, these dictionaries below are outputted on console:

{'price__sum': Decimal('150.00')}
{'price__sum': Decimal('150.00')}

And, you can change the default key price__sum to priceSum for price column as shown below:

from django.db.models import Sum
                                        # ↓ Here
print(ItemPrice.objects.all().aggregate(priceSum=Sum('price')))
print(ItemPrice.objects.aggregate(priceSum=Sum('price')))
                                  # ↑ Here

Then, the default key is changed as shown below:

{'priceSum': Decimal('150.00')}
{'priceSum': Decimal('150.00')}