heroku-buildpack-python/bin/steps/django

#!/usr/bin/env bash

# This script serves as the Django build step of the
# [**Python Buildpack**](https://github.com/heroku/heroku-buildpack-python) 
# compiler. 
# 
# A [buildpack](http://devcenter.heroku.com/articles/buildpacks) is an 
# adapter between a Python application and Heroku's runtime.
#
# This script is invoked by [`bin/compile`](/).

# ## Sanity Checks
#

# Reject a Django app that appears to be packaged incorrectly.
if [ -f settings.py ]; then
  echo " !     Django app must be in a package subdirectory"
  exit 1
fi

echo "-----> Injecting Django settings..."


SETTINGS_FILE=$(find . -maxdepth 2 -type f -name 'settings.py' | head -1)
PROJECT=$(dirname $SETTINGS_FILE)

echo "Injecting code into $SETTINGS_FILE to read from DATABASE_URL" | indent

cat >>$SETTINGS_FILE <<EOF

import os
import sys
import urlparse

# Register database schemes in URLs.
urlparse.uses_netloc.append('postgres')
urlparse.uses_netloc.append('mysql')

try:

    # Check to make sure DATABASES is set in settings.py file.
    # If not default to {}

    if 'DATABASES' not in locals():
        DATABASES = {}

    if 'DATABASE_URL' in os.environ:
        url = urlparse.urlparse(os.environ['DATABASE_URL'])

        # Ensure default database exists.
        DATABASES['default'] = DATABASES.get('default', {})

        # Update with environment configuration.
        DATABASES['default'].update({
            'NAME': url.path[1:],
            'USER': url.username,
            'PASSWORD': url.password,
            'HOST': url.hostname,
            'PORT': url.port,
        })
        if url.scheme == 'postgres':
            DATABASES['default']['ENGINE'] = 'django.db.backends.postgresql_psycopg2'

        if url.scheme == 'mysql':
            DATABASES['default']['ENGINE'] = 'django.db.backends.mysql'
except Exception:
    print 'Unexpected error:', sys.exc_info()

EOF