Django split settings module

settings__init__.py

# settings convention from:
# https://code.djangoproject.com/wiki/SplitSettings#SettingInheritancewithHierarchy
import os, pwd

# certain keys we want to merge instead of copy
merge_keys = ('INSTALLED_APPS', 'MIDDLEWARE_CLASSES')

def deep_update(from_dict, to_dict):
    for (key, value) in from_dict.iteritems():
        if key in to_dict.keys() and isinstance(to_dict[key], dict) and isinstance(value, dict):
            deep_update(value, to_dict[key])
        elif key in merge_keys:
            if not key in to_dict:
                to_dict[key] = ()
            to_dict[key] = to_dict[key] + from_dict[key]
        else:
            to_dict[key] = value

# this should be one of prod, qa, staging, dev. Default to dev for safety.
env = os.environ.get('APP_ENV', 'dev')

imported_modules = set()

# try to load user specific settings
modules = ('common', env)
try:
    uid = pwd.getpwuid(os.getuid())[0]
    modules = modules + (uid,)
except KeyError:
    uid = None

current = __name__
for module_name in modules:
    try:
        module = getattr(__import__(current, globals(), locals(), [module_name]), module_name)
    except ImportError, e:
        print 'ERROR: Unable to import %s configuration: %s' % (module_name, e)
        raise
    except AttributeError, e:
        if module_name == uid:
            print 'WARNING: Unable to import settings.%s; does it exist?' % (module_name,)
        else:
            raise

    # create a local copy of this module's settings
    module_settings = {}
    for setting in dir(module):
        # all django settings are uppercase, so this ensures we
        # are only processing settings from the dir() call
        if setting == setting.upper():
            module_settings[setting] = getattr(module, setting)
    deep_update(module_settings, locals())

    imported_modules.add(module_name)

#print locals() # for debugging