12factor/django snippet for configging django via enviroment variables

settings.py

import environ
root = environ.Path(__file__) - 2
# SECURITY WARNING: don't run with debug turned on in production!
env = environ.Env(DEBUG=(bool, True),) # set default values and casting
environ.Env.read_env() # reading .env file

ALLOWED_HOSTS = ['localhost', *env("ALLOWED_HOSTS", default="").split(",")]

SITE_ROOT = root()

DEBUG = env('DEBUG') # False if not in os.environ
TEMPLATE_DEBUG = DEBUG

DATABASES = {
    'default': env.db(default="sqlite:///"+root("db.sqlite3")),
}

public_root = root.path('public/')

MEDIA_ROOT = public_root('media')
MEDIA_URL = '/media/'
STATIC_ROOT = public_root('static')
STATIC_URL = '/static/'


CACHES = {
    'default': env.cache(default="pymemcache://"),
}

# SECURITY WARNING: keep the secret key used in production secret!
SECRET_KEY = env('SECRET_KEY',default=None)
if not SECRET_KEY:
    SECRET_FILE = root('secret.txt')
    try:
        SECRET_KEY = open(SECRET_FILE).read().strip()
    except IOError:
        import random
        SECRET_KEY = ''.join([random.SystemRandom().choice('abcdefghijklmnopqrstuvwxyz0123456789!@#$%^&*(-_=+)') for i in range(50)])
        try:
            secret = open(SECRET_FILE, 'w')
            secret.write(SECRET_KEY)
            secret.close()
        except IOError:
            print("Can not store secret key file, using ephemeral secret key, which will cause session errors")
            print("Please either specify a `SECRET_KEY` in your env, or ensure `{}` if writeable.".format(SECRET_FILE))