[Numpy-discussion] take(..., out=something) does not seem to work

27 Apr 2007

      Hi,

Either I have completely misunderstood what the out= arg to the take
function is supposed to do, or there is a bug in numpy 1.0.2, as
demonstrated below.

First, some initialization:

    In [1]: from numpy import *

    In [2]: a=arange(12).reshape((3,4))

    In [3]: a
    Out[3]: 
    array([[ 0,  1,  2,  3],
           [ 4,  5,  6,  7],
           [ 8,  9, 10, 11]])

Let's try take without an output argument:

    In [4]: take(a, [0,2], axis=1)
    Out[4]: 
    array([[ 0,  2],
           [ 4,  6],
           [ 8, 10]])

Good. Now let's create an array of the right size and dtype, and use
it for output:

    In [5]: b = zeros_like(_)

    In [6]: take(a, [0,2], axis=1, out=b)
    Out[6]: 
    array([[ 0,  2],
           [ 4,  6],
           [ 8, 10]])

    In [7]: b
    Out[7]: 
    array([[0, 0],
           [0, 0],
           [0, 0]])

It seems that b was not affected at all.

-- 
Jouni K. Seppänen
http://www.iki.fi/jks