show the number of contacts for each list

cartero/admin.py

 # -*- coding: utf-8 -*-
 from django.conf.urls import patterns
 from django.contrib import admin
+from django.db.models import Count
 from django.utils.translation import ugettext_lazy as _
 
 from .models import Contact, EmailTemplate, Campaign, ExcludedEmail,\
@@ -48,11 +49,21 @@ admin.site.register(Contact, ContactAdmin)
 class ContactListAdmin(admin.ModelAdmin):
     list_display = [
         'name',
+        'num_contacts',
     ]
     search_fields = [
         'name',
     ]
 
+    def get_queryset(self, request):
+        qs = super(ContactListAdmin, self).get_queryset(request)
+        qs = qs.annotate(num_contacts=Count('contacts'))
+        return qs
+
+    def num_contacts(self, obj):
+        return ("%s" % (obj.num_contacts, ))
+    num_contacts.short_description = '# Contacts'
+
 
 @admin.register(ContactInList)
 class ContactInListAdmin(admin.ModelAdmin):