Lagrange polynomial calc, first three

Callaghans.py

'''

Lagrange polynomial

'''

def L(X, x, y):
    l1, l2, l3 = L1(X, x, y), L2(X, x, y), L3(X, x, y)
    return l1, l2, l3, l1 - l3, l2 - l3

def L1(X, x, y):
    l = list()
    l.append((X-x[1])/(x[0]-x[1])*y[0])
    l.append((X-x[0])/(x[1]-x[0])*y[1])
    return sum(map(float,l))
    
def L2(X, x, y):
    l = list()
    l.append(((X-x[1])*(X-x[2]))/((x[0]-x[1])*(x[0]-x[2]))*y[0])
    l.append(((X-x[0])*(X-x[2]))/((x[1]-x[0])*(x[1]-x[2]))*y[1])
    l.append(((X-x[0])*(X-x[1]))/((x[2]-x[0])*(x[2]-x[1]))*y[2])
    return sum(l)
    
def L3(X, x, y):
    l = list()
    l.append(((X-x[1])*(X-x[2])*(X-x[3]))/((x[0]-x[1])*(x[0]-x[2])*(x[0]-x[3]))*y[0])
    l.append(((X-x[0])*(X-x[2])*(X-x[3]))/((x[1]-x[0])*(x[1]-x[2])*(x[1]-x[3]))*y[1])
    l.append(((X-x[0])*(X-x[1])*(X-x[3]))/((x[2]-x[0])*(x[2]-x[1])*(x[2]-x[3]))*y[2])
    l.append(((X-x[0])*(X-x[1])*(X-x[2]))/((x[3]-x[0])*(x[3]-x[1])*(x[3]-x[2]))*y[3])
    return sum(l)
    
X = 0.08
x = [0.05, 0.1, 0.15, 0.2]
y = [-4.171, -4.133, -4.0845, -4.0240]
print(list(map(lambda x: '{0:.10f}'.format(x), L(X, x, y))))