Django, the web framework for perfectionists with deadlines, is based on a single settings Python module defined in a environment variable. However, these settings could be organized into three categories:

• settings that are very common and that can be kept as-is for most projects (USE_TZ = True or MEDIA_URL = '/media/'),
• settings that are specific to your project but common to all instances of your project (like INSTALLED_APPS),
• settings that are installation-dependent (DATABASE_PASSWORD, …)

Moreover, there are dependencies between settings. For example, ADMIN_EMAIL, ALLOWED_HOSTS and CSRF_COOKIE_DOMAIN depend on the same domain name of your site, and SESSION_COOKIE_SECURE and CSRF_COOKIE_SECURE can be set only when you use TLS. df_config allows to use functions to dynamically define these settings using some other settings as parameters.

Finally, df_config dynamically merges several sources to define the final settings:

• :mod:df_config.config.defaults that aims at providing good default values,
• yourproject.defaults for your project-specific settings,
• /etc/yourproject/settings(.py|.ini) for installation-dependent settings,
• environment variables are also read if you prefer to use them.

df_config also defines settings that should be valid for most sites, based on common installed Django apps.

You can define a list of settings that are read from a traditionnal text configuration file (.ini format <https://docs.python.org/3/library/configparser.html>_). Finally, df_config also searches for environment variables, or local_settings.py and local_settings.ini setting files in the working directory.

df_config works with:

• Python 3.6+,
• Django 2.0+.

python -m pip install df_config

df_config assumes that your project has a main module yourproject. Then you just have two steps to do:

• update your manage.py file:

#!/usr/bin/env python
from df_config.manage import manage, set_env

set_env(module_name="yourproject")
if __name__ == "__main__":
    manage()

• copy your current settings (as-is) into yourproject/defaults.py,

You can take a look to the resulting settings and from which source they are read:

python3 manage.py config python -v 2

If you want a single settings file, you can also create it:

python3 manage.py config python --filename settings.py

You should the entry point in your setup.py file:

entry_points = {"console_scripts": ["yourproject-ctl = df_config.manage:manage"]}

Once installed, the command yourproject-ctl (in fact, you can change ctl by anything without hyphen) executes the standard maanage command.

First, you can provide sensible defaults settings in yourproject.py and overwrite the dev settings in local_settings.py. Then real things can begin: For example, imagine that you currently have the following settings:

LOG_DIRECTORY = '/var/myproject/logs'
STATIC_ROOT = '/var/myproject/static'
MEDIA_ROOT = '/var/myproject/media'
FILE_UPLOAD_TEMP_DIR = '/var/myproject/tmp'

If you change the base directory /var/myproject, four variables needs to be changed (and you will forget to change at least one). Now, you can write:

LOCAL_PATH = '/var/myproject'
LOG_DIRECTORY = '{LOCAL_PATH}/logs'
STATIC_ROOT = '{LOCAL_PATH}/static'
MEDIA_ROOT = '{LOCAL_PATH}/media'
FILE_UPLOAD_TEMP_DIR = '{LOCAL_PATH}/tmp'

Now, you just have to redefine LOCAL_PATH; but you can even go slightly further:

from df_config.config.dynamic_settings import Directory
LOCAL_PATH = Directory('/var/myproject')
LOG_DIRECTORY = Directory('{LOCAL_PATH}/logs')
STATIC_ROOT = Directory('{LOCAL_PATH}/static')
MEDIA_ROOT = Directory('{LOCAL_PATH}/media')
FILE_UPLOAD_TEMP_DIR = Directory('{LOCAL_PATH}/tmp')

If you run the check command, you will be warned for missing directories, and the collectstatic and migrate commands will attempt to create them. Of course, you still have settings.MEDIA_ROOT == '/var/myproject/media' in your code, when settings are loaded.

You can use more complex things, instead of:

SERVER_BASE_URL = 'http://www.example.com'
SERVER_NAME = 'www.example.com'
USE_SSL = False
ALLOWED_HOSTS = ['www.example.com']
CSRF_COOKIE_DOMAIN = 'www.example.com'

You could just write:

from urllib.parse import urlparse
from df_config.config.dynamic_settings import CallableSetting

SERVER_BASE_URL = 'http://www.example.com'
SERVER_NAME = CallableSetting(lambda x: urlparse(x['SERVER_BASE_URL']).hostname, 'SERVER_BASE_URL')
USE_SSL = CallableSetting(lambda x: urlparse(x['SERVER_BASE_URL']).scheme == 'https', 'SERVER_BASE_URL')
ALLOWED_HOSTS = CallableSetting(lambda x: [urlparse(x['SERVER_BASE_URL']).hostname], 'SERVER_BASE_URL')
CSRF_COOKIE_DOMAIN = CallableSetting(lambda x: urlparse(x['SERVER_BASE_URL']).hostname, 'SERVER_BASE_URL')

Your user probably prefer use .ini files instead of Python ones. By default, df_config searches for a list INI_MAPPING into the module yourproject.iniconf or uses df_config.iniconf.INI_MAPPING.

from df_config.config.fields import ConfigField
INI_MAPPING = [ConfigField("global.server_url", "SERVER_BASE_URL", help_str="Public URL of your website.", env_name="SERVER_BASE_URL")]

Some specialized classes are available in df_config.config.fields: CharConfigField, IntegerConfigField, FloatConfigField, ListConfigField, BooleanConfigField, ChoiceConfigFile. You can also pickup some predefined list in df_config.iniconf.

You can also use environment variables instead of an .ini file (only for values in the INI_MAPPING list):

export SERVER_URL=http://www.example-2.com
python3 manage.py config python -v 2 | grep SERVER_BASE_URL

You can check the current config as a .ini file or as environment variables:

export SERVER_URL=http://www.example-2.com
python3 manage.py config env
python3 manage.py config ini

By default, any str is assumed to be a template string: for example, LOG_DIRECTORY = '{LOCAL_PATH}/logs' needs LOCAL_PATH to be defined. So, if one of your setting include such values, it need to be encapsulated:

from df_config.config.dynamic_settings import RawValue
LOG_DIRECTORY = RawValue('{LOCAL_PATH}/logs')

Other dynamic classes are:

from df_config.config.dynamic_settings import Directory, AutocreateFileContent, SettingReference, CallableSetting, ExpandIterable
from df_config.guesses.misc import generate_secret_key, secure_hsts_seconds
DIRNAME = Directory("/tmp/directory")
# creates /tmp/directory with collectstatic/migrate commands, otherwise you have a warning 
SECRET_KEY = AutocreateFileContent("{LOCAL_PATH}/secret_key.txt", generate_secret_key, mode=0o600, use_collectstatic=False,use_migrate=True)
# if the file does not exist, SECRET_KEY = generate_secret_key()
# if the file does exist, SECRET_KEY is equal to its content
# if the migrate command is called and the file does not exist, it is created and the result of generate_secret_key() is written to it
TEMPLATE_DEBUG = SettingReference('DEBUG')
# TEMPLATE_DEBUG is always equal to DEBUG, even if DEBUG is defined in another file
SECURE_HSTS_SECONDS = CallableSetting(secure_hsts_seconds, "USE_SSL")
# the secure_hsts_seconds is called with a dict that contains the currently resolved settings
# at least USE_SSL is present in this dict (maybe some other values are also defined)
# the list of required settings can be directly set as an attribute of the callable:
# secure_hsts_seconds.required_settings = ["USE_SSL"]
# SECURE_HSTS_SECONDS = CallableSetting(secure_hsts_seconds)
INSTALLED_APPS = ["django.contrib.admin", ..., ExpandIterable("EXTRA_APPS"), "django.contrib.auth"]
# EXTRA_APPS must be a list, whose values are inserted in the final valaues

You can choose the application server used in production:

DF_SERVER = "gunicorn"  # "gunicorn" or "daphne"

A new Django command server is available and launches gunicorn or daphne. The application and the listen address/port are specified so you do no have to set them.

Environment variable names have been chosen to be compatible with the Heroku default environment:

• SECRET_KEY: should set it in your app.json file
• DATABASE_URL: automatically set by the "heroku-postgresql" addon
• PORT: set by default
• HEROKU_APP_NAME: you should set it in your app.json file

A few well-known Django applications are automatically detected and added to the list of INSTALLED_APPS:

• django-pipeline
• django-debug-toolbar
• django-allauth
• whitenoise
• django-csp
• celery
• df_websockets
• django-channels
• django-auth-ldap
• django-cors-headers
• django-hosts
• django-minio-storage
• django—pam
• django-prometheus
• django-radius
• django-redis-sessions
• django-smart-selects
• sentry.io

Defaults settings are also proposed so these applications should be working out of the box.