SciPy

scipy.special.gammaincc

scipy.special.gammaincc(x1, x2[, out]) = <ufunc 'gammaincc'>

y=gammaincc(a,x) returns the complemented incomplete gamma integral defined as 1 / gamma(a) * integral(exp(-t) * t**(a-1), t=x..inf) = 1 - gammainc(a,x). a must be positive and x must be >= 0.