Wilson得分间隔的Python实现？

Reddit使用Wilson得分区间进行评论排名，可以在此处找到说明和python实现

#Rewritten pre from /r2/r2/lib/db/_sorts.pyxfrom math import sqrtdef confidence(ups, downs):    n = ups + downs    if n == 0:        return 0    z = 1.0 #1.44 = 85%, 1.96 = 95%    phat = float(ups) / n    return ((phat + z*z/(2*n) - z * sqrt((phat*(1-phat)+z*z/(4*n))/n))/(1+z*z/n))