heroku-buildpack-python/Readme.md

virtualenv

pip

Django settings.py

Sets up a db for every ENV ${NAME}_URL => postgres:// var: DATABASES["DATABASE"] DATABASES["SHARED_DATABASE"] DATABASES["HEROKU_POSTGRESQL_ONYX"]

Aliases DATABASE_URL to default database: DATABASES["default"] = DATABASES["DATABASE"]

Injected right after DATABASES = {...}