scipy.special
scipy.special.
pdtri
Inverse to pdtr vs m
pdtr
Returns the Poisson variable m such that the sum from 0 to k of the Poisson density is equal to the given probability y: calculated by gammaincinv(k+1, y). k must be a nonnegative integer and y between 0 and 1.
scipy.special.pdtrc
scipy.special.pdtrik