[Numpy-discussion] boolean masks & lists

Lisandro Dalcin dalcinl@gmail....
Tue Nov 6 08:22:44 CST 2007


Mmm...
It looks as it 'mask' is being inernally converted from
[True, False, False, False, True]
to
[1, 0, 0, 0, 1]

so your are finally getting

x[1], x[0], x[0], x[0], x[1]


On 11/5/07, John Hunter <jdh2358@gmail.com> wrote:
> A colleague of mine just asked for help with a pesky bug that turned
> out to be caused by his use of a list of booleans rather than an array
> of booleans as his logical indexing mask.  I assume this is a feature
> and not a bug, but it certainly surprised him:
>
> In [58]: mask = [True, False, False, False, True]
>
> In [59]: maska = n.array(mask, n.bool)
>
> In [60]: x = arange(5)
>
> In [61]: x[mask]
> Out[61]: array([1, 0, 0, 0, 1])
>
> In [62]: x[maska]
> Out[62]: array([0, 4])
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>


-- 
Lisandro Dalcín
---------------
Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC)
Instituto de Desarrollo Tecnológico para la Industria Química (INTEC)
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
PTLC - Güemes 3450, (3000) Santa Fe, Argentina
Tel/Fax: +54-(0)342-451.1594


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