Django do a simple group by / count statement

Question

Let's say I have the following:

 MY_CHOICES = ( (1, "Choice 1"), (2, "Choice 2"), (3, "Choice 3"), ) class MyModel(models.Model): name = models.CharField(max_length=64, ) category = models.CharField(max_length=4, choices=MY_CHOICES)

Now, what I'd like to do is group by category and get the number of instances for each group. For instance, I'd like to get a result like this:

 Choice 1: 31 Instances Choice 2: 4 Instances Choice 3: 2 Intances

This can be done with the following query:

 group_by_category = MyModel.objects.values('category').distinct().annotate(count=Count('category'))

The above works however because the values() will return a ValueQuerySet (which contains dicts instead of MyModel instances). So I am not able to use "get_category_display" to output "Choice 1", "Choice 2" etc, but I can only print the numbers.

Is there a DRY way to be able to use the get_category_display method ?

I know that I can add the display value myself using a for loop to modify each dict (if category=='1' then its display value is "Choice 1" etc) however I don't feel that's DRY enough.

It could be better to have a second model for your categories instead of using choices. — RodrigoOlmo
– RodrigoOlmo, Commented Jun 14, 2014 at 8:41
@RodrigoOlmo I am aware of that however I don't want to change my database schema right now. — Serafeim
– Serafeim, Commented Jun 14, 2014 at 8:44

Krzysztof Szularz · Accepted Answer · 2014-06-15 00:19:11Z

1

>>> dict(MY_CHOICES)[1] "Choice 1"

Why distinct()? Does it do anything in this case?

answered Jun 15, 2014 at 0:19

Krzysztof Szularz

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