GROUP BY and Select MAX from each group in Django, 2 queries

gistfile1.py

'''
given a Model with:

   category    = models.CharField(max_length=32, choices=CATEGORY_CHOICES)
   pubdate     = models.DateTimeField(default=datetime.now)
   <other fields>

Fetch the item from each category with the latest pubdate.

''' 

model_max_set = Model.objects.values('category').annotate(max_pubdate=Max('pubdate')).order_by()

# THE "ONE LINE BECAUSE FUNCTIONAL PROGRAMMING IS AWESOME BLAH BLAH BLAH" EDITION 
# kudos to tkaemming

model_set = Model.objects.filter( reduce(lambda a,b:a|b, [(Q(category__exact=pair['category']) & Q(pubdate=pair['max_pubdate'])) for pair in model_max_set ])      )