[Numpy-discussion] Faster than ndindex?

Pauli Virtanen pav@iki...
Sat Dec 4 13:16:45 CST 2010


On Sat, 04 Dec 2010 19:00:43 +0000, Eleftherios Garyfallidis wrote:
[clip]
> I am using ndindex and then a for loop. Is there a better/faster way?

Yes:

import numpy as np
from numpy import newaxis

x = np.zeros((200, 200, 200, 3))
x[...,0] = np.arange(200)[:,newaxis,newaxis]
x[...,1] = np.arange(200)[newaxis,:,newaxis]
x[...,2] = np.arange(200)[newaxis,newaxis,:]
x[1,3,2]
# -> array([ 1.,  3.,  2.])

Depending on what you use this array for, it's possible that you can 
avoid constructing it (and use broadcasting etc. instead).

-- 
Pauli Virtanen



More information about the NumPy-Discussion mailing list