Django: construct a QuerySet inside a view?

Question

I have models as follows:

class Place(models.Model):
    name = models.CharField(max_length=300)  
class Person(models.Model):
    name = models.CharField(max_length=300) 
class Manor(models.Model):
    place = models.ManyToManyField(Place, related_name="place"))  
    lord = models.ManyToManyField(Person, related_name="lord")  
    overlord = models.ManyToManyField(Person, related_name="overlord")

I want to get all the Places attached with the relation 'lord' to a particular person, and then get the centre, using a GeoDjango method. This is as far as I've got:

person = get_object_or_404(Person, namesidx=namesidx)
manors = Manor.objects.filter(lord=person)
places = []
for manor in manors:
    place_queryset = manor.place.all()
    for place in place_queryset: 
        places.append(place)  
if places.collect():
    centre = places.collect().centroid

However, this gives me:

AttributeError at /name/208460/gamal-of-shottle/
'list' object has no attribute 'collect'

Can I either (a) do this in a more elegant way to get a QuerySet of places back directly, or (b) construct a QuerySet rather than a list in my view?

Thanks for your help!

Daniel Roseman · Accepted Answer · 2011-01-11 14:39:12Z

1

The way you're doing this, places is a standard list, not a QuerySet, and collect is a method that only exists on GeoDjango QuerySets.

You should be able to do the whole query in one go by following the relations with the double-underscore syntax:

places = Place.objects.filter(manor__lord=person)

Note that your use of related_name="place" on the Manor.place field is very confusing - this is what sets the reverse attribute from Place back to Manor, so it should be called manors.

edited Jan 11, 2011 at 14:39

answered Jan 11, 2011 at 13:41

Daniel Roseman

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