def lift_calc(PPV, PRE):
    """
    Calculate Lift score.

    :param PPV: Positive predictive value (PPV)
    :type PPV: float
    :param PRE: Prevalence
    :type PRE: float
    :return: lift score as float
    """
    try:
        return PPV / PRE
    except (ZeroDivisionError, TypeError):
        return "None"