numpy-discussion

[Numpy-discussion] please comment on scalar types

[Sebastian H. <ha...@ms...>]

Hi!
I have a record array with a field 'mode'
Mode is a small integer that I use to choose a "PixelType"
So I did:
>>> print PixelTypes[ mode ]
TypeError: tuple indices must be integers
>>> pdb.pm()
> /home/haase/PrLinN64/Priithon/Mrc.py(813)MrcMode2numType()
-> return PixelTypes[ mode ]
(Pdb) p mode
1
(Pdb) p type(mode)
<type 'int32scalar'>
(Pdb) p isinstance(mode, int)
False

Since numpy introduced special scalar types a simple statement like this 
doesn't work anymore !  Would it work if int32scalar was derived from int ? I 
actually thought it was ...

Comments ?

- Sebastian Haase

Re: [Numpy-discussion] please comment on scalar types

[Travis O. <oli...@ie...>]

Sebastian Haase wrote:
> Hi!
> I have a record array with a field 'mode'
> Mode is a small integer that I use to choose a "PixelType"
> So I did:
>   
>>>> print PixelTypes[ mode ]
>>>>         
> TypeError: tuple indices must be integers
>   
>>>> pdb.pm()
>>>>         
>> /home/haase/PrLinN64/Priithon/Mrc.py(813)MrcMode2numType()
>>     
> -> return PixelTypes[ mode ]
> (Pdb) p mode
> 1
> (Pdb) p type(mode)
> <type 'int32scalar'>
> (Pdb) p isinstance(mode, int)
> False
>
> Since numpy introduced special scalar types a simple statement like this 
> doesn't work anymore !  Would it work if int32scalar was derived from int ? I 
> actually thought it was ...
>   
It does sub-class from int unless you are on a system where a c-long is 
64-bit then int64scalar inherits from int.

On my 32-bit system:

isinstance(array([1,2,3])[0],int)  is true.



-Travis

Re: [Numpy-discussion] please comment on scalar types

[Sebastian H. <ha...@ms...>]

Travis Oliphant wrote:
> Sebastian Haase wrote:
>> Hi!
>> I have a record array with a field 'mode'
>> Mode is a small integer that I use to choose a "PixelType"
>> So I did:
>>   
>>>>> print PixelTypes[ mode ]
>>>>>         
>> TypeError: tuple indices must be integers
>>   
>>>>> pdb.pm()
>>>>>         
>>> /home/haase/PrLinN64/Priithon/Mrc.py(813)MrcMode2numType()
>>>     
>> -> return PixelTypes[ mode ]
>> (Pdb) p mode
>> 1
>> (Pdb) p type(mode)
>> <type 'int32scalar'>
>> (Pdb) p isinstance(mode, int)
>> False
>>
>> Since numpy introduced special scalar types a simple statement like this 
>> doesn't work anymore !  Would it work if int32scalar was derived from int ? I 
>> actually thought it was ...
>>   
> It does sub-class from int unless you are on a system where a c-long is 
> 64-bit then int64scalar inherits from int.
> 
> On my 32-bit system:
> 
> isinstance(array([1,2,3])[0],int)  is true.
> 
> 
> 
> -Travis
I see -
yes I forgot - that test was indeed run on 64bit Linux.

And that automatically implies that there a  32bit-int cannot be used in 
place of a "normal python integer" !?
I could see wanting to use int16 or event uint8 as a tuple index.
Logically a small type would be save to use in place of a bigger one ...


- Sebastian

Re: [Numpy-discussion] please comment on scalar types

[Travis O. <oli...@ee...>]

Sebastian Haase wrote:

>Travis Oliphant wrote:
>  
>
>And that automatically implies that there a  32bit-int cannot be used in 
>place of a "normal python integer" !?
>I could see wanting to use int16 or event uint8 as a tuple index.
>Logically a small type would be save to use in place of a bigger one ...
>  
>

That is the purpose behind the __index__ attribute I added to Python 2.5 
(see PEP 357).  This allows all the scalar integers to be used in place 
of integers inside of Python.

-Travis