How to create identity matrix with numpy

Question

How do I create an identity matrix with numpy? Is there a simpler syntax than

numpy.matrix(numpy.identity(n))

Answer 1

Also np.eye can be used to create an identity array (In).

For example,

>>> np.eye(2, dtype=int)
array([[1, 0],
       [0, 1]])
>>> np.eye(3, k=1)
array([[ 0.,  1.,  0.],
       [ 0.,  0.,  1.],
       [ 0.,  0.,  0.]])

Answer 2

I don't think there is a simpler solution. You can do it slightly more efficiently, though:

numpy.matrix(numpy.identity(n), copy=False)

This avoids unnecessarily copying the data.

Answer 3

Here's a simpler syntax:

np.matlib.identity(n)

And here's an even simpler syntax that runs much faster:

In [1]: n = 1000
In [2]: timeit np.matlib.identity(n)
100 loops, best of 3: 8.78 ms per loop
In [3]: timeit np.matlib.eye(n)
1000 loops, best of 3: 695 us per loop