[Numpy-discussion] int and long issues

Mads Ipsen madsipsen@gmail....
Thu Jan 10 05:29:41 CST 2013


Sebastian - thanks - very helpful.

Best regards,

Mads



On 10/01/2013 12:06, Sebastian Berg wrote:
> On Thu, 2013-01-10 at 11:32 +0100, Mads Ipsen wrote:
>> Hi,
>>
>> I find this to be a little strange:
>>
>>      x = numpy.arange(10)
>>      isinstance(x[0],int)
>>
>> gives True
>>
>>      y = numpy.where(x < 5)[0]
>>      isinstance(y[0],int)
>>
>> gives False
>>
>>      isinstance(y[0],long)
>>
> Check what type(x[0])/type(y[0]) prints, I expect these are very
> different, because the default integer type and the integer type used
> for indexing (addressing memory in general) are not necessarily the
> same. And because of that, `y[0]` probably simply isn't compatible to
> the datatype of a python integer for your hardware and OS (for example
> for me, your code works). So on python 2 (python 3 abolishes int and
> makes long the only integer, so this should work as expected there) you
> have to just check both even in the python context, because you can
> never really know (there may be some nice trick for that, but not sure).
> And if you want to allow for rare 0d arrays as well (well they are very
> rare admittingly)... it gets even a bit hairier.
>
>
>> gives True
>>
>> Specs: Python 2.7.2, numpy-1.6.1, Win7, 64 bit
>>
>> Best regards,
>>
>> Mads
>> -- 
>> +-----------------------------------------------------+
>> | Mads Ipsen                                          |
>> +----------------------+------------------------------+
>> | Gåsebæksvej 7, 4. tv |                              |
>> | DK-2500 Valby        | phone:          +45-29716388 |
>> | Denmark              | email:  mads.ipsen@gmail.com |
>> +----------------------+------------------------------+
>>
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-- 
+-----------------------------------------------------+
| Mads Ipsen                                          |
+----------------------+------------------------------+
| Gåsebæksvej 7, 4. tv |                              |
| DK-2500 Valby        | phone:          +45-29716388 |
| Denmark              | email:  mads.ipsen@gmail.com |
+----------------------+------------------------------+



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