formula langranga (interpolysia)

X=[1,2,3,4,5]
Y=[1,8,27,64,125]
cur_X= 2
def L(X,Y,cur_X):
    res=0.0
    n=len(X)
    for i in range(n):
        l_i=1.0
        for j in range(n):
            if i==j:
                 continue
            l_i*=(cur_X-float (X[j]))/(X[i]-X[j])
        res+=Y[i]*l_i;
    return res
print L(X,Y,cur_X)