scipy.special.betainc

scipy.special.betainc(x1, x2, x3[, out])

y=betainc(a,b,x) returns the incomplete beta integral of the arguments, evaluated from zero to x:

gamma(a+b) / (gamma(a)*gamma(b)) * integral(t**(a-1) (1-t)**(b-1), t=0..x).