def inverse_weight(distance, num=1.0, const=0.1):
    """
    权重函数: 距离的逆.
    :param distance: 距离
    :type distance: float
    :param num: 分子
    :type num: float
    :param const: 常量
    :type const: float
    :return: 权重值
    """
    return num / (distance + const)