import math


def DP_calc(TPR, TNR):
    """
    Calculate DP (Discriminant power).

    :param TNR: specificity or true negative rate
    :type TNR : float
    :param TPR: sensitivity, recall, hit rate, or true positive rate
    :type TPR : float
    :return: DP as float
    """
    try:
        X = TPR / (1 - TPR)
        Y = TNR / (1 - TNR)
        return (math.sqrt(3) / math.pi) * (math.log(X, 10) + math.log(Y, 10))
    except Exception:
        return "None"