Django’s signal dispatcher is a solid way to interact with your models without mucking up the code. This is especially useful for the contrib applications, namely django.contrib.comments. All Django models, by default, have several dispatches: class_prepared, pre_init, post_init, pre_save, post_save, pre_delete, post_delete. This allows us to attach functionality at several points in the model instance’s life.

After receiving a number of spam comments on my blog (not a significant number, but annoying nonetheless), I decided I wanted to be notified when a comment was created. Here is a bit of code I created for a simple email, placed in my project’s __init__.py:

from django.contrib.comments.models import Comment, FreeComment
from django.core.mail import send_mail
from django.dispatch import dispatcher
from django.db.models import signals

def comment_notification(sender, instance):
    subject = 'New Comment on %s' % instance.get_content_object().title
    msg = 'Comment text:\n\n%s' % instance.comment
    send_mail(subject, msg, 'noreply@example.com', ['email@example.com'])

dispatcher.connect(comment_notification, sender=FreeComment, signal=signals.post_save)
dispatcher.connect(comment_notification, sender=Comment, signal=signals.post_save)

This type of dispatch system enhances granularity and modularity, thereby allowing developers to modify the default actions of Django’s models without having to modify Django itself. Signals aren’t in the main documentation yet, but if you would like to read more check out this wiki page.

P.S., If you want real comment utilities I recommend Ubernostrum’s django-comment-utils package, which includes “template tags for common operations, a custom manager with useful querying functionality for models which use comments, and a generic comment-moderation system”.