def get_todays_file_path(self):
        """ path to today's cached file """
        datum = Datum()
        datum.today()
        today = datum.get_iso_date_string()

        return self.__get_rate_file_path(today)
    def get_yesterdays_file_path(self):
        """ Full path to the today's rates file. """
        datum = Datum()
        datum.yesterday()
        yesterday = datum.get_iso_date_string()

        return self.__get_rate_file_path(yesterday)