[Numpy-discussion] where() on mac/pc return different things
James Battat
jbattat at cfa.harvard.edu
Wed Jan 23 18:54:37 EST 2008
Robert,
Thanks for solving that puzzle! I'll get our group on the same 1.0.x
numpy release.
Take care,
James
**************************
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Dept. of Astronomy
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**************************
On Wed, 23 Jan 2008, Robert Kern wrote:
> James Battat wrote:
> > Hi,
> >
> > numpy.where() returns different things on my windowsXP machine than on my
> > collaborator's mac osx machine.
> >
> > For example, consider:
> > >>> import numpy
> > >>> a = numpy.array([1,2,3,4])
> > >>> b = numpy.where( a > 2 )
> >
> > On WindowsXP (python 2.4.2, numpy 1.0.1), I get:
> > >>> print b
> > (array([2, 3]), )
> > >>> print b[0]
> > [2 3]
> >
> > While in OSX (python 2.4.3, numpy 0.9.6), he gets:
> > >>> print b
> > [2, 3]
> > >>> print b[0]
> > 2
> >
> > This matters because we use where() to get indices to loop over. On the
> > mac you can then loop through the b array:
> >
> > for item in b:
> > if b > 5:
> > print 'hi'
> >
> > But this approach fails on a pc because:
> > if b > 5:
> > >>> ValueError: The truth value of an array with more than one element
> > >>> is ambiguous. Use a.any() or a.all()
> >
> >
> > I'd like to avoid having to do:
> > if mac:
> > b = numpy.where( a > 5)
> > if pc:
> > b = numpy.where( a > 5)[0]
> >
> > Has anybody else notice dealt with this? Is this a mac/pc difference or a
> > numpy 1.01 vs. numpy 0.9.6 difference?
>
> The latter. Before the 1.0 release, we tried to make it clear that we were still
> experimenting with the APIs and that they might change up until 1.0 got released.
>
> --
> Robert Kern
>
> "I have come to believe that the whole world is an enigma, a harmless enigma
> that is made terrible by our own mad attempt to interpret it as though it had
> an underlying truth."
> -- Umberto Eco
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