conf.py

from django.conf import settings as django_settings


class Setting(object):
    def __init__(self, name):
        self.name = name

    def __get__(self, instance, owner):
        return self.get_value()

    def __set__(self, instance, value):
        raise TypeError("Cannot assign value to setting.")

    def get_value(self):
        raise NotImplementedError


class DefaultSetting(Setting):
    def __init__(self, name, default):
        super(DefaultSetting, self).__init__(name)
        self.default = default

    def get_value(self):
        return getattr(django_settings, self.name, self.default)


class VaultSetting(Setting):
    def __init__(self, name):
        self.name = name

    def __get__(self, instance, owner):
        return self.get_value()

    def __set__(self, instance, value):
        raise TypeError("Cannot assign value to vault.")

    def get_value(self):
        return self.get_vault_key(self.name)

    def get_vault_key(self, name):
        print("go vault setting", name)
        return name


class CachedVaultSetting(VaultSetting):
    def __init__(self, name):
        super(CachedVaultSetting, self).__init__(name)
        self.value = None

    def get_value(self):
        if self.value is None:
            self.value = self.get_vault_key(self.name)
        return self.value


class AppSettings(object):
    _instances = {}

    def __new__(cls, *args, **kwargs):
        if cls not in cls._instances:
            cls._instances[cls] = super(AppSettings, cls).__new__(cls, *args, **kwargs)
        return cls._instances[cls]

    def __getattr__(self, name):
        return getattr(django_settings, name)


class Settings(AppSettings):
    VAULT_SETTING = CachedVaultSetting('VAULT_KEY')
    DEFAULT_SETTING = DefaultSetting('TIMEOUT', 10)


settings = Settings()