[Numpy-discussion] RFC: out of range slice indexes
Robert Kern
robert.kern at gmail.com
Mon Jan 14 14:44:19 EST 2008
Neal Becker wrote:
> I've never liked that python silently ignores slices with out of range
> indexes. I believe this is a source of bugs (it has been for me). It goes
> completely counter to the python philosophy.
>
> I vote to ban them from numpy.
>>>> from numpy import array
>>>> x = array (xrange (10))
>>>> x[11]
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> IndexError: index out of bounds
>>>> x[:12] = 2
>>>> x
> array([2, 2, 2, 2, 2, 2, 2, 2, 2, 2])
>>>> len (x)
> 10
>
> Silently ignoring the error x[:12] is a bad idea, IMO. If it meant to
> _extend_ x to have lenght 12, at least _that_ would be reasonable (but I'm
> not advocating that position).
>
> I believe that out of bounds indexes should always throw IndexError. We
> can't change that in Python now, but maybe we can in numpy.
-1. Regardless of the merits if we had a blank slate, there is code that depends
on this, specifically my code. It simplifies certain operations that would
otherwise need tedious special case-handling.
--
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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