def default_prompt(prompt, default=None):
    """
    Prompt the user for input. If they press enter, return the default.

    :param str prompt: Prompt to display to user (do not include default value)
    :param str default: Default return value
    :return: Value entered or default
    :rtype: str or None
    """
    value = str(input(prompt + " [default: %s]: " % str(default)))
    return default if value == '' else value