django-modelforms

This project came about because our reusable administration has to deal with related models that have unique_together constraints (and modern UniqueConstraint) that were not being properly validated by the default implementation.

It occurs because our forms don't show the related field, it's not something we want the user to be able to edit. This has the nasty side-effect of excluding the related field from validation checks, so uniqueness (with respect to the related field) is not tested.

The form therefore validates, and a database update is attempted - only to fail when integrity constraints are enforced by the backend.

Installation

pip install django-modelforms

Or with uv:

uv add django-modelforms

Usage

Simply use modelforms.forms.ModelForm instead of django.forms.ModelForm:

from modelforms.forms import ModelForm

class BookForm(ModelForm):
    class Meta:
        model = Book
        fields = ['title', 'rrp']

This will properly validate both legacy unique_together constraints and modern UniqueConstraint definitions in your model's Meta.constraints.

Supported Django and Python Versions

• Django 4.2, 5.2, 6.0
• Python 3.10, 3.11, 3.12, 3.13

Why?

Django bug #13091 was filed in March 2010 and still has not been fixed.

There has been discussion on the mailing lists and a number of patches proposed, but none have been accepted.

To stop encountering this in our projects we decided to write something generic that can easily be used without having to wait for an upstream fix.

Development

This project uses uv and tox for development:

# Install development dependencies
uv sync

# Run tests
uv run tox

# Run tests for a specific environment
uv run tox -e py312-django52

# Run linting
uv run tox -e lint

License

BSD-3-Clause