[Numpy-discussion] __array_wrap__

Robert Kern robert.kern@gmail....
Tue Sep 29 13:48:14 CDT 2009


On Tue, Sep 29, 2009 at 13:35, Charles R Harris
<charlesr.harris@gmail.com> wrote:
>
> On Tue, Sep 29, 2009 at 12:23 PM, Robert Kern <robert.kern@gmail.com> wrote:
>>
>> On Tue, Sep 29, 2009 at 13:09, Charles R Harris
>> <charlesr.harris@gmail.com> wrote:
>> >
>> >
>> > On Tue, Sep 29, 2009 at 11:00 AM, Neal Becker <ndbecker2@gmail.com>
>> > wrote:
>> >>
>> >> fixed_pt arrays need to apply the overflow_policy after operations
>> >> (overflow_policy could be clip, or throw exception).
>> >>
>> >> I thought __array_wrap__ would work for this, but it seems to not be
>> >> called
>> >> when I need it.  For example:
>> >>
>> >> In [13]: obj
>> >> Out[13]: fixed_pt_array([  0,  32,  64,  96, 128])
>> >>
>> >> In [14]: obj*100 < this should overflow
>> >> enter: [  0  32  64  96 128] << on entry into __array_wrap
>> >> enter: [0 32 64 96 128]
>> >> exit: [  0  32  64  96 128]
>> >> Out[14]: fixed_pt_array([    0,  3200,  6400,  9600, 12800])
>> >>
>> >> Apparantly, obj*100 is never passed to array_wrap.
>> >>
>> >> Is there another way I can do this?
>> >>
>> > I believe array wrap has to be explicitly called after the fact.
>>
>> Ufuncs call __array_wrap__ implicitly.
>>
>
> Thanks for the info. How do they decide which one to call?

The .__array_priority__ attribute.

-- 
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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