[Numpy-discussion] Casting Bug or a "Feature"?

Patrick Marsh patrickmarshwx@gmail....
Wed Jan 16 21:43:22 CST 2013


Thanks, everyone for chiming in.  Now that I know this behavior exists, I
can explicitly prevent it in my code. However, it would be nice if a
warning or something was generated to alert users about the inconsistency
between var += ... and var = var + ...


Patrick


---
Patrick Marsh
Ph.D. Candidate / Liaison to the HWT
School of Meteorology / University of Oklahoma
Cooperative Institute for Mesoscale Meteorological Studies
National Severe Storms Laboratory
http://www.patricktmarsh.com


On Wed, Jan 16, 2013 at 7:24 PM, Nathaniel Smith <njs@pobox.com> wrote:

> This is separate from the scalar casting thing. This is a disguised
> version of the discussion about what we should do with implicit casts
> caused by assignment:
>   into_array[i] = 0.5
>
> Traditionally numpy just happily casts this stuff, possibly mangling data
> in the process, and this has caused many actual bugs in user code. In 1.6
> some of these assignments cause errors, but we reverted this in 1.7 because
> this was also breaking things. Supposedly we also deprecated these at the
> same time, with an eye towards making them errors eventually, but I'm not
> sure we did this properly, and our carrying rules need revisiting in any
> case.
>
> (Sorry for lack of links to earlier discussion; traveling and on my phone.)
>
> -n
> On 16 Jan 2013 16:42, "Chris Barker - NOAA Federal" <chris.barker@noaa.gov>
> wrote:
>
>> Patrick,
>>
>> Not a bug but is it a mis-feature?
>>
>> See the recent thread: "Do we want scalar casting to behave as it does
>> at the moment"
>>
>> In short, this is an complex issue with no easy answer...
>>
>> -Chris
>>
>>
>> --
>>
>> Christopher Barker, Ph.D.
>> Oceanographer
>>
>> Emergency Response Division
>> NOAA/NOS/OR&R            (206) 526-6959   voice
>> 7600 Sand Point Way NE   (206) 526-6329   fax
>> Seattle, WA  98115       (206) 526-6317   main reception
>>
>> Chris.Barker@noaa.gov
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>
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