using namespace arma;

vec eigval;
mat eigvec;

// C++11 initialization
mat A = { 1, -1, 0, -1, 2, -1, 0, -1, 1};

eig_sym(eigval, eigvec, A);
eigvec.print("Eigen Vectors");

Eigen Vectors
-5.7735e-01  -7.071068e-01  0.4082483
-5.7735e-01  9.714451e-e17  -0.8164966
-5.7735e-01  7.017068e-01   0.4082483

import numpy as np
w,v = np.linalg.eig(np.array([[1,-1,0],[-1,2,-1],[0,-1,1]]))
v

array([[ -4.08248290e-01,  -7.07106781e-01,   5.77350269e-01],
       [  8.16496581e-01,   2.61214948e-16,   5.77350269e-01],
       [ -4.08248290e-01,   7.07106781e-01,   5.77350269e-01]])

eigen(matrix(c(1,-1,0,-1,2,-1,0,-1,1), 3, byrow=TRUE)$vectors

-4.082483e-01  -7.071068e-01   5.773503e-01
 8.164966e-01   9.420555e-16   5.773503e-01
-4.082483e-01   7.071068e-01   5.773503e-01