Torsional Angle.py

import math

class Points(object):
    def __init__(self, x, y, z):
        self.x = x
        self.y = y
        self.z = z

    def __sub__(self, other):
        return Points(self.x - other.x, self.y - other.y, self.z - other.z)

    def dot(self, other):
        return self.x * other.x + self.y * other.y + self.z * other.z

    def cross(self, other):
        return Points(self.y*other.z - self.z*other.y, self.z*other.x - self.x*other.z, self.x*other.y - self.y*other.x)

    def absolute(self):
        return pow((self.x ** 2 + self.y ** 2 + self.z ** 2), 0.5)

if __name__ == '__main__':
    points = list()
    for i in range(4):
        a = list(map(float, input().split()))
        points.append(a)

    a, b, c, d = Points(*points[0]), Points(*points[1]), Points(*points[2]), Points(*points[3])
    x = (b - a).cross(c - b)
    y = (c - b).cross(d - c)
    angle = math.acos(x.dot(y) / (x.absolute() * y.absolute()))

    print("%.2f" % math.degrees(angle))