On Apr 30, 11:26 am, Derek <gamesb...@gmail.com> wrote:
> I would like to be able to filter a query set based on a calculated date
> value. Googling did not bring up anything obvious.
>
> As close as I can express it in "pseudo syntax", I'd like to do something
> along these lines:
>
> import datetime
> from dateutil.relativedelta import *
> today = datetime.now()
> MyModel.objects.filter( (my_date_field + relativedelta(months =
> +my_month_field))__lt = today )
>
> i.e. compare one date with another - the second is calculated using a date
> field and a second numeric field (value representing months).
>
> The above syntax does not work - I am not sure how to code the calculation
> part...
>
> Thanks
> Derek
>
The calculation needs to go on the other side of the expression. The
left-hand side is a keyword, so can't be a calculation. And you can
use the F() function to get the value of your months field. I think
this should work:
from django.db.models import F
MyModel.objects.filter(my_date_field__lt=today -
relativedelta(months=F('my_month_field')))
--
DR.
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