Aggregation functions returns AttributeError: 'Sum' object has no attribute 'lookup'

Question

I'm trying out the aggregation functions, and I get this strange results (latest official Django 1.2 release). Here's the model:

class Reputation(models.Model):
    user = models.ForeignKey(User)
    modifier = models.IntegerField()
    activity = models.ForeignKey(Activity)

This is what I get:

In [37]: Reputation.objects.aggregate(r=Sum('modifier'))
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)

C:\Data\Development\django_projects\oko\lib\site-packages\django\db\models\manager.pyc in aggregate(self, *args, **kwargs)
    142
    143     def aggregate(self, *args, **kwargs):
--> 144         return self.get_query_set().aggregate(*args, **kwargs)
    145
    146     def annotate(self, *args, **kwargs):

C:\Data\Development\django_projects\oko\lib\site-packages\django\db\models\query.pyc in aggregate(self, *args, **kwargs)
    315         for (alias, aggregate_expr) in kwargs.items():
    316             query.add_aggregate(aggregate_expr, self.model, alias,
--> 317                 is_summary=True)
    318
    319         return query.get_aggregation(using=self.db)

C:\Data\Development\django_projects\oko\lib\site-packages\django\db\models\sql\query.pyc in add_aggregate(self, aggregate, model, alias, is_summary)
    929         """
    930         opts = model._meta
--> 931         field_list = aggregate.lookup.split(LOOKUP_SEP)
    932         if len(field_list) == 1 and aggregate.lookup in self.aggregates:
    933             # Aggregate is over an annotation

AttributeError: 'Sum' object has no attribute 'lookup'

Where have you imported Sum from?

DrMeers
– DrMeers

2011-03-17 22:04:27 +00:00
Commented Mar 17, 2011 at 22:04 — DrMeers
– DrMeers, Commented Mar 17, 2011 at 22:04
Good question; see my answer, below.

Mathieu Dhondt
– Mathieu Dhondt

2011-03-17 22:32:06 +00:00
Commented Mar 17, 2011 at 22:32 — Mathieu Dhondt
– Mathieu Dhondt, Commented Mar 17, 2011 at 22:32

user212218 · Accepted Answer · 2013-08-18 01:07:01Z

6

Make sure you import the correct Sum:

from django.db.models import Sum

If you import django.db.models.sql.aggregates.Sum, you will continue to see that error.

answered Aug 18, 2013 at 1:07

user212218

Sign up to request clarification or add additional context in comments.

Comments

Yuji 'Tomita' Tomita · Accepted Answer · 2011-03-17 22:15:03Z

4

Judging by the fact that your post is the sole mention of that error message via google searching, and that I can reproduce your error by using a random class called Sum into an aggregation function, I think you have a local definition of Sum in your code.

You're on line 37 of your console session. Try starting anew, from django.db.models import Sum, from myproject.myapp.models import Reputation, then the query.

answered Mar 17, 2011 at 22:15

Yuji 'Tomita' Tomita

119k32 gold badges287 silver badges247 bronze badges

1 Comment

Yuji 'Tomita' Tomita Over a year ago

Ohh, I didn't about that. I'm sure this will help people googling!

Liz Rice · Accepted Answer · 2012-11-22 08:57:33Z

1

I got the same error by failing to include the aggregation function within an annotation i.e.

wrong:

Person.objects.annotate(ave_score='starred_in__score')

right:

Person.objects.annotate(ave_score=Avg('starred_in__score'))

A stupid mistake on my part, but thought I'd document it here in case it helps anyone else.

answered Nov 22, 2012 at 8:57

Liz Rice

5896 silver badges9 bronze badges

Comments

Yushin Washio · Accepted Answer · 2019-02-11 09:10:02Z

1

This is not exactly what the question is about, but I encountered almost the same error (no attribute 'lookup') using F in annotate. The import was correct, but its use in annotate was added in Django 1.8 whilst I am using Django 1.7. You’d need to use filter instead if you’re also using that old Django release.

answered Feb 11, 2019 at 9:10

Yushin Washio

7499 silver badges12 bronze badges

Collectives™ on Stack Overflow

Aggregation functions returns AttributeError: 'Sum' object has no attribute 'lookup'

4 Answers 4

Comments

1 Comment

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

1 Comment

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related