django conditionally filtering objects

Question

I would like to retrieve a bunch of rows from my database using a set of filters.

I was wondering if conditional filter is applicable in django. That is, \"filter if

Answer 1

They are several approach to your issue. One approach is to play with Complex lookups with Q objects

from django.db.models import Q

user = User.objects.get(pk=1)
category = Category.objects.get(pk=1)

f1 = Q( user=user, date=now() )
f_cat_is_none = Q( category__isnull = True )
f_cat_is_not_none = Q( category=category )

todays_items = Item.objects.filter( f1 & ( f_cat_is_none | f_cat_is_not_none ) )

I don't right understand in your answer if this is the query you are looking for, but, with this example you can compose easily your own query.

Edited due OP comment

category__isnull == True means that, in database, the item has not an associated category. Perhaps the query you are looking for is:

from django.db.models import Q

user_pk = 1
category_pk = 1  #some times None

f = Q( user__pk = user_pk, date=now() )
if category_pk is not None:
  f &= Q( category__pk = category_pk )

todays_items = Item.objects.filter( f  )

This is only a code sample, fit it to your requirements. Be careful with single _ and double __.