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

josef.pktd@gmai... josef.pktd@gmai...
Wed Jan 16 21:54:40 CST 2013


On Wed, Jan 16, 2013 at 10:43 PM, Patrick Marsh
<patrickmarshwx@gmail.com> wrote:
> 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 + ...

Since I also got bitten by this recently in my code, I fully agree.
I could live with an exception for lossy down casting in this case.

Josef

>
>
>
> 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
>>> _______________________________________________
>>> NumPy-Discussion mailing list
>>> NumPy-Discussion@scipy.org
>>> http://mail.scipy.org/mailman/listinfo/numpy-discussion
>>
>>
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