How to aggregate values by month

Hello!

I'm having an issue to make complex queries in django. My problem is, I have a model where I have the sales and I need to make a report showing the sales amount per month, by the way I made this query:

init_date = datetime.date(datetime.now()-timedelta(days=365))
ends_date = datetime.date(datetime.now())
sales = Sale.objects.filter(date_created__range=(init_date,ends_date)).values(date_created__month).aggregate(total_sales=Sum('total_value'))

At the first line I get the today's date past one year
after this I got the today date

at sales I'm trying to between a range get the sales amount grouped by month, but unfortunatelly I was unhappy on this, because this error appeared:

global name 'date_created__month' is not defined

At date_created is the field where I store the information about when the sale was done., the __moth was a tentative to group by this by month.

So, my question: how to do that thing without using a raw sql query and not touching on database independence?

Thanks so much!

Rogério Carrasqueira

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e-mail: rogerio.carrasqueira@gmail.com
skype: rgcarrasqueira
MSN: rcarrasqueira@hotmail.com
ICQ: 50525616
Tel.: (11) 7805-0074

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