n-dimensional angles in python

angle.py

import numpy as np


def unit_vector(vector):
    """ Returns the unit vector of the vector.  """
    return vector / np.linalg.norm(vector)


def angle_between(vector_1, vector_2):
    """ Returns the angle in radians between vectors 'vector_1' and 'vector_2'::

            >>> angle_between((1, 0, 0), (0, 1, 0))
            1.5707963267948966
            >>> angle_between((1, 0, 0), (1, 0, 0))
            0.0
            >>> angle_between((1, 0, 0), (-1, 0, 0))
            3.141592653589793
    """
    vector_1_u = unit_vector(vector_1)
    vector_2_u = unit_vector(vector_2)
    angle = np.arccos(np.dot(vector_1_u, vector_2_u))
    if np.isnan(angle):
        if (vector_1_u == vector_2_u).all():
            return 0.0
        else:
            return np.pi
    return angle