How to extend Django settings variables with local_settings.py

local_settings.py

# Code from Mikko Hellsing:
# http://www.robgolding.com/blog/2010/05/03/extending-settings-variables-with-local_settings-py-in-django/#comment-51863642

def get_setting(setting):
    import settings
    return getattr(settings, setting)

INSTALLED_APPS = get_setting('INSTALLED_APPS') + ('debug_toolbar', )
MIDDLEWARE_CLASSES = get_setting('MIDDLEWARE_CLASSES') + ('debug_toolbar.middleware.DebugToolbarMiddleware',)
INTERNAL_IPS = ('127.0.0.1',)