Compute the angle between vector x and y

def angle_between_vectors(x, y):
    """ Compute the angle between vector x and y """
    dp = dot_product(x, y)
    if dp == 0:
        return 0
    xm = magnitude(x)
    ym = magnitude(y)
    return math.acos(dp / (xm*ym)) * (180. / math.pi)