Question

Sorry this is basic, but I’m new to Python and Django.

I have a list of users who have performed an action that is being saved in a separate table. I want to show a list of these users, sorted by how many times they’ve taken the other action.

I understand how to get the counts:

users = User.objects.all()
for user in users:
    print user.action_set.count()

And I understand how to show the counts in my template:

{% for user in users %}
    {{ user.action_set.count }}
{% endfor %}

But I’m not sure how to have it sort the users by the count of the action set.

Answer 1

Annotate / Aggregation
http://docs.djangoproject.com/en/dev/topics/db/aggregation/

from django.db.models import Count
users = User.objects.annotate(action_count=Count('action')).order_by('action_count')
# note that this also saves your extra query PER user object.

{% for user in users %}
   {{ user.action_count }}
{% endfor %}

For future reference, if you couldn’t sort by the DB, you can python sort any list…

my_list.sort(key=lambda x: x[2])

my_list.sort(key=lambda x: x.method())

Very useful.