def dipole_moment(r_array, charge_array):
    '''Return the dipole moment of a neutral system.
    '''
    return np.sum(r_array * charge_array[:, np.newaxis], axis=0)
def dipole_moment ( r_array , charge_array ) : return np . sum ( r_array * charge_array [ : , np . newaxis ] , axis = 0 )
Return the dipole moment of a neutral system.