Re: [Numpy-discussion] boolean masks & lists
John Hunter 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]) > The issues is how to determine what behavior is desired and how to manage that with all the possibilities. Right now the rule is that only boolean arrays are treated as masks and integer arrays mean indexing. Lists are always interpreted as integer indexing (except in certain special cases where the list has slice objects in it).Changing this to something like: lists are interpreted either as boolean or integer arrays, may be reasonable, but I don't see how we can change it until 1.1 because the rule has already been specified and is consistent if not obvious in this simple case. The question is: is anybody using boolean lists specifically according to the rule in place now? -Travis ___ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
Re: [Numpy-discussion] boolean masks & lists
On Nov 6, 2007 7:22 AM, Lisandro Dalcin <[EMAIL PROTECTED]> wrote: > 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] That would be my guess as well. And, it looks wrong to me. Given that array(mask) gives you the boolean mask, there's every expectation to expect the the list and array cases should be the same. I would file a bug report. > > > > On 11/5/07, John Hunter <[EMAIL PROTECTED]> 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]) > > ___ > > Numpy-discussion mailing list > > Numpy-discussion@scipy.org > > http://projects.scipy.org/mailman/listinfo/numpy-discussion > > > > > -- > 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 > ___ > Numpy-discussion mailing list > Numpy-discussion@scipy.org > http://projects.scipy.org/mailman/listinfo/numpy-discussion > -- . __ . |-\ . . [EMAIL PROTECTED] ___ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
Re: [Numpy-discussion] boolean masks & lists
On Nov 6, 2007 8:22 AM, Lisandro Dalcin <[EMAIL PROTECTED]> wrote: > Mmm... > It looks as it 'mask' is being inernally converted from > [True, False, False, False, True] > to > [1, 0, 0, 0, 1] Yep, clearly. The question is: is this the desired behavior because it leads to a "silent failure" for people who are expecting sequences of booleans to behave like arrays of booleans. JDH ___ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
Re: [Numpy-discussion] boolean masks & lists
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 <[EMAIL PROTECTED]> 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]) > ___ > Numpy-discussion mailing list > Numpy-discussion@scipy.org > http://projects.scipy.org/mailman/listinfo/numpy-discussion > -- 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 ___ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
[Numpy-discussion] boolean masks & lists
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]) ___ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
