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“how to get value and calculate sum in django” Code Answersum_a = sum([item. column for item in queryset]) # Definitely takes more memory. sum_b = queryset. aggregate(Sum('column')).
Django-filter is a generic, reusable application to alleviate writing some of the more mundane bits of view code. Specifically, it allows users to filter down a queryset based on a model's fields, displaying the form to let them do this. Adding a FilterSet with filterset_class. Using the filterset_fields shortcut.
The Django ORM is a convenient way to extract data from the database, and the annotate() clause that you can use with QuerySets is also a useful way to dynamically generate additional data for each object when the data is being extracted.
You're probably looking for aggregate
from django.db.models import Sum
ItemPrice.objects.aggregate(Sum('price'))
# returns {'price__sum': 1000} for example
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.
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