Skip to main content

Django fieldsignals simply makes it easy to tell when the fields on your model have changed.

Project description

[![Build Status](](

# Introduction

django-fieldsignals simply makes it easy to tell when the fields on your model have changed.

Often model updates are quite expensive. Sometimes the expensive operations
are very rare. This makes it tempting to put the update logic in a view,
rather than in a save() method or in a signal receiver:

# A bad example. Don't do this!
def edit_poll(request, poll_id):

# ...

if form.cleaned_data['poll_name'] !=

That's a bad idea, because your model consistency is now dependent on your view.

Instead, use django-fieldsignals:

from fieldsignals import pre_save_changed

def update_poll_slug(sender, instance, **kwargs):
instance.slug = slugify(

pre_save_changed.connect(update_poll_slug, sender=Poll, fields=['name'])

In case you want to know what changed, django-fieldsignals even tells you the old and
new values of your fields:

from fieldsignals import pre_save_changed

def print_all_field_changes(sender, instance, changed_fields=None, **kwargs):
for field, (old, new) in changed_fields.items():
print "%s changed from %s to %s" % (, old, new)

pre_save_changed.connect(print_all_field_changes, sender=Poll)

# Installation

1. This library is on PyPI so you can install it with:

pip install django-fieldsignals

or from github:

pip install 'git+'

2. Add `"fieldsignals"` to your `INSTALLED_APPS` setting like this:


3. Add some signals!

# Where should my signals code live?

Field signals must be connected after the django apps are ready.
So putting signal connectors at the bottom of your models file, or other random places won't work.

The best place to connect fieldsignals is an [`AppConfig.ready()` handler](

# Notes

* Currently no support for `ManyToManyField` or reverse side of `ForeignKey` (one to many).

Project details

Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Filename, size & hash SHA256 hash help File type Python version Upload date
django_fieldsignals-0.4.0-py2.py3-none-any.whl (7.1 kB) Copy SHA256 hash SHA256 Wheel 2.7
django-fieldsignals-0.4.0.tar.gz (7.0 kB) Copy SHA256 hash SHA256 Source None

Supported by

Elastic Elastic Search Pingdom Pingdom Monitoring Google Google BigQuery Sentry Sentry Error logging AWS AWS Cloud computing DataDog DataDog Monitoring Fastly Fastly CDN SignalFx SignalFx Supporter DigiCert DigiCert EV certificate StatusPage StatusPage Status page