>>> import numpy 
>>> numpy.eye(3) 
array([[ 1., 0., 0.], 
    [ 0., 1., 0.], 
    [ 0., 0., 1.]]) 
>>> numpy.zeros(3) 
array([ 0., 0., 0.]) 
>>> numpy.ones(3) 
array([ 1., 1., 1.]) 
>>> x1 = numpy.array((1, 2, 3)) 
>>> x1 
array([1, 2, 3]) 
>>> x2 = numpy.array([4, 5, 6]) 
>>> x2 
array([4, 5, 6]) 
>>> x3 = numpy.array((x1, x2)) 
>>> x3 
array([[1, 2, 3], 
    [4, 5, 6]]) 
>>> x4 = x3.reshape(2, 3) 
>>> x4 
array([[1, 2, 3], 
    [4, 5, 6]]) 
>>> x4 = x3.reshape(3, 2) 
>>> x4 
array([[1, 2], 
    [3, 4], 
    [5, 6]]) 
>>> x5 = numpy.row_stack(x1, x2) 
Traceback (most recent call last): 
 File "<stdin>", line 1, in <module> 
TypeError: vstack() takes exactly 1 argument (2 given) 
>>> x5 = numpy.row_stack((x1, x2)) 
>>> x5 
array([[1, 2, 3], 
    [4, 5, 6]]) 
>>> x6 = numpy.row_stack([x1, x2]) 
>>> x6 
array([[1, 2, 3], 
    [4, 5, 6]]) 
>>> x7 = numpy.row_stack((x6, x2)) 
>>> x7 
array([[1, 2, 3], 
    [4, 5, 6], 
    [4, 5, 6]]) 
>>> x7[0] 
array([1, 2, 3]) 
>>> x7[1] 
array([4, 5, 6]) 
>>> x7[2] 
array([4, 5, 6]) 
>>> x8 = numpy.column_stack([x1, x2, x1, x2]) 
>>> x8 
array([[1, 4, 1, 4], 
    [2, 5, 2, 5], 
    [3, 6, 3, 6]]) 
>>> x8[0] 
array([1, 4, 1, 4]) 
>>> x8[1] 
array([2, 5, 2, 5]) 
>>> x8[2] 
array([3, 6, 3, 6]) 
>>> x8[3] 
Traceback (most recent call last): 
 File "<stdin>", line 1, in <module> 
IndexError: index 3 is out of bounds for axis 0 with size 3 
>>> x8[0][3] 
4 
>>> 

print np.ones((1,4))*2