django-pydantic-settings

Use pydantic settings management to simplify configuration of Django settings.

Very much a work in progress, but reads the standard DJANGO_SETTINGS_MODULE environment variable (defaulting to pydantic_settings.settings.PydanticSettings) to load a sub-class of pydantic_settings.Settings. All settings (that have been defined in pydantic_settings.Settings) can be overridden with environment variables. A special DatabaseSettings class is used to allow multiple databases to be configured simply with DSNs. In theory, django-pydantic-settings should be compatible with any version of Django that runs on Python 3.6.1+ (which means Django 1.11 and on), but is only tested against officially supported versions (currently 2.2, 3.0, 3.1, and 3.2).

Note: as of django-pydantic-settings 0.4.0, Pydantic 1.8+ is required, which means Python 3.6.1+ is also required. If you need to use Python 3.6, you'll need to stick with django-pydantic-settings <0.4.0.

Installation & Setup

Install django-pydantic-settings:

pip install django-pydantic-settings

Modify your Django project's manage.py file to use django-pydantic-settings, it should look something like this:

#!/usr/bin/env python
"""Django's command-line utility for administrative tasks."""
import sys

from pydantic_settings import SetUp


def main():
    """Run administrative tasks."""
    SetUp().configure()

    try:
        from django.core.management import execute_from_command_line
    except ImportError as exc:
        raise ImportError(
            "Couldn't import Django. Are you sure it's installed and "
            "available on your PYTHONPATH environment variable? Did you "
            "forget to activate a virtual environment?"
        ) from exc
    execute_from_command_line(sys.argv)


if __name__ == "__main__":
    main()

Your wsgi.py and/or asgi.py files will need to be modified similarly, and look something like this:

from django.core.wsgi import get_wsgi_application

from pydantic_settings import SetUp

SetUp().configure()
application = get_wsgi_application()

The SetUp class will automatically look for the standard DJANGO_SETTINGS_MODULE environment variable, read it, confirm that it points to an existing Python module, and load that module. Your DJANGO_SETTINGS_MODULE variable should point to a pydantic_settings.settings.PydanticSettings sub-class (though technically any Python class that defines a dict() method which returns a Python dictionary of key/value pairs matching the required Django settings will work). Calling the configure() method will then use the specified module to configure your project's Django settings.

Required settings

There are no settings that must be configured in order to use Django with django-pydantic-settings. All of the possible settings defined by Django (Settings Reference) are configured in the pydantic_settings.settings.PydanticSettings class, using their normal default values provided by Django, or a reasonable calculated value. Settings worth thinking about are ROOT_URLCONF and WSGI_APPLICATION, which, unless otherwise specified, are calculated based on your DJANGO_SETTINGS_MODULE assuming that you're using the default Django project layout a provided by django-admin.py startproject. So, for example, if your DJANGO_SETINGS_MODULE is set to my_awesome_project.settings.PydanticSettingsSubclass, then ROOT_URLCONF and WSGI_APPLICATION will be set to my_awesome_project.urls and my_awesome_project.wsgi respectively. This default behavior can be overridden by simply specifying ROOT_URLCONF:str = 'the_actual_urlconf' and WSGI_APPLICATION:str = 'the_actual_wsgi_file.application' in your PydanticSettings sub-class. Alternatively, rather than individually settings the ROOT_URLCONF and WSGI_APPLICATION settings, you can set BASE_DIR, and that will be used instead of DJANGO_SETTINGS_MODULE.

The other setting worth thinking about is SECRET_KEY. By default, SECRET_KEY is automatically generated using Django's own get_random_secret_key() function. This will work just fine, though as it will be re-calculated every time your PydanticSettings sub-class is instantiated, you should set this to somethign static if you're using Django's authentication and don't want to lose your session every time the server is restarted.

Database configuration

By defining multiple DatabaseDsn attributes of the DatabaseSettings class, you can easily configure one or more database connections with environment variables. DSNs are parsed using dj-database-url. In order to support Google Cloud SQL database connections from within Google Cloud Run, the DatabaseDsn type will detect and automatically escape DSN strings of the form postgres://username:password@/cloudsql/project:region:instance/database so that they can be properly handled by dj-database-url.

class DatabaseSettings(BaseSettings):
    default: DatabaseDsn = Field(env="DATABASE_URL")
    secondary: DatabaseDsn = Field(env="SECONDARY_DATABASE_URL")

❯ DATABASE_URL=postgres://username:password@/cloudsql/project:region:instance/database SECONDARY_DATABASE_URL=sqlite:///foo poetry run python settings_test/manage.py shell
Python 3.9.1 (default, Jan 12 2021, 16:45:25) 
[GCC 8.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>> from rich import print
>>> from django.conf import settings
>>> print(settings.DATABASES)
{
    'default': {
        'NAME': 'database',
        'USER': 'username',
        'PASSWORD': 'password',
        'HOST': '/cloudsql/project:region:instance',
        'PORT': '',
        'CONN_MAX_AGE': 0,
        'ENGINE': 'django.db.backends.postgresql_psycopg2'
    },
    'secondary': {'NAME': 'foo', 'USER': '', 'PASSWORD': '', 'HOST': '', 'PORT': '', 'CONN_MAX_AGE': 0, 'ENGINE': 'django.db.backends.sqlite3'}
}
>>> 

Sentry configuration

django-pydantic-settings provides built-in functionality for configuring your Django project to use Sentry. The simplest way to use this is to inherit from pydantic_settings.sentry.SentrySettings rather than pydantic_settings.settings.PydanticSettings. This adds the setting SENTRY_DSN, which uses the pydantic_settings.sentry.SentryDsn type. This will automatically be set according to the DJANGO_SENTRY_DSN environment variable, and expects a Sentry DSN (obviously). It validates that the provided DSN is a valid URL, and then automatically initializes the Sentry SDK using the built-in DjangoIntegration. Using this functionality required sentry-sdk to be installed, which will be included automatically if you install django-pydantic-settings[sentry].