numpy-discussion

[Numpy-discussion] arr.dtype.kind is 'i' for dtype=unit !?

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

Hi,
What are the possible values of 
arr.dtype.kind ?

It seems that signed and unsigned are considered to be the same "kind" 
>>> arr=N.arange(10,dtype=N.uint)
>>> arr.dtype.kind
'i'
>>> arr.dtype.itemsize
8
(OK - this is just showing off our amd64 linux ;-) )

How can I distinguish signed from unsigned without having to list all possible 
cases explicitly ?

Thanks,
Sebastian Haase

Re: [Numpy-discussion] arr.dtype.kind is 'i' for dtype=unit !?

[Albert S. <fu...@gm...>]

Hello all

> -----Original Message-----
> From: num...@li... [mailto:numpy-
> dis...@li...] On Behalf Of Sebastian Haase
> Sent: 19 September 2006 19:24
> To: Discussion of Numerical Python
> Subject: [Numpy-discussion] arr.dtype.kind is 'i' for dtype=unit !?
> 
> Hi,
> What are the possible values of
> arr.dtype.kind ?
> 
> It seems that signed and unsigned are considered to be the same "kind"
> >>> arr=N.arange(10,dtype=N.uint)
> >>> arr.dtype.kind
> 'i'
> >>> arr.dtype.itemsize
> 8
> (OK - this is just showing off our amd64 linux ;-) )
> 
> How can I distinguish signed from unsigned without having to list all
> possible
> cases explicitly ?

How about sctypes?

In [16]: numpy.sctypes.keys()
Out[17]: ['int', 'float', 'uint', 'complex', 'others']

So this should work:

sometype in numpy.sctypes['uint']
sometype in numpy.sctypes['int']

Cheers,

Albert

Re: [Numpy-discussion] arr.dtype.kind is 'i' for dtype=unit !?

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

Sebastian Haase wrote:
> Hi,
> What are the possible values of 
> arr.dtype.kind ?
>
> It seems that signed and unsigned are considered to be the same "kind" 
>   
>>>> arr=N.arange(10,dtype=N.uint)
>>>> arr.dtype.kind
>>>>         
> 'i'
>   
>>>> arr.dtype.itemsize
>>>>         
> 8
> (OK - this is just showing off our amd64 linux ;-) )
>
> How can I distinguish signed from unsigned without having to list all possible 
> cases explicitly ?
>
>
>   
Hmm....  This is a problem.   There is a 'u' kind for unsigned integers.  

On my system I get 'u' when running the code you just gave.

Can anybody on a 64-bit system confirm?

-Travis

Re: [Numpy-discussion] arr.dtype.kind is 'i' for dtype=unit !?

[Scott R. <sr...@nr...>]

On Tuesday 19 September 2006 14:46, Travis Oliphant wrote:
> Sebastian Haase wrote:
> > Hi,
> > What are the possible values of
> > arr.dtype.kind ?
> >
> > It seems that signed and unsigned are considered to be the same
> > "kind"
> >
> >>>> arr=N.arange(10,dtype=N.uint)
> >>>> arr.dtype.kind
> >
> > 'i'
> >
> >>>> arr.dtype.itemsize
> >
> > 8
> > (OK - this is just showing off our amd64 linux ;-) )
> >
> > How can I distinguish signed from unsigned without having to list all
> > possible cases explicitly ?
>
> Hmm....  This is a problem.   There is a 'u' kind for unsigned
> integers.
>
> On my system I get 'u' when running the code you just gave.
>
> Can anybody on a 64-bit system confirm?

I'm on 64-bit Debian:

In [11]: arr=N.arange(10,dtype=N.uint)

In [12]: arr.dtype.kind
Out[12]: 'u'

In [13]: arr.dtype.itemsize
Out[13]: 4

In [14]: arr=N.arange(10,dtype=N.long)

In [15]: arr.dtype.kind
Out[15]: 'i'

In [16]: arr.dtype.itemsize
Out[16]: 8


Scott

-- 
Scott M. Ransom            Address:  NRAO
Phone:  (434) 296-0320               520 Edgemont Rd.
email:  sr...@nr...             Charlottesville, VA 22903 USA
GPG Fingerprint: 06A9 9553 78BE 16DB 407B  FFCA 9BFA B6FF FFD3 2989

Re: [Numpy-discussion] arr.dtype.kind is 'i' for dtype=unit !?

[Scott R. <sr...@nr...>]

> > Can anybody on a 64-bit system confirm?
>
> I'm on 64-bit Debian:
>
> In [11]: arr=N.arange(10,dtype=N.uint)
>
> In [12]: arr.dtype.kind
> Out[12]: 'u'
>
> In [13]: arr.dtype.itemsize
> Out[13]: 4
>
> In [14]: arr=N.arange(10,dtype=N.long)
>
> In [15]: arr.dtype.kind
> Out[15]: 'i'
>
> In [16]: arr.dtype.itemsize
> Out[16]: 8

Ack!  That was on the wrong machine (32-bit Debian).  Here is the 64-bit 
version:

In [2]: arr=N.arange(10,dtype=N.uint)

In [3]: arr.dtype.kind
Out[3]: 'u'

In [4]: arr.dtype.itemsize
Out[4]: 8

In [5]: arr=N.arange(10,dtype=N.long)

In [6]: arr.dtype.kind
Out[6]: 'i'

In [7]: arr.dtype.itemsize
Out[7]: 8

Sorry about that,

Scott

-- 
Scott M. Ransom            Address:  NRAO
Phone:  (434) 296-0320               520 Edgemont Rd.
email:  sr...@nr...             Charlottesville, VA 22903 USA
GPG Fingerprint: 06A9 9553 78BE 16DB 407B  FFCA 9BFA B6FF FFD3 2989

Re: [Numpy-discussion] arr.dtype.kind is 'i' for dtype=unit !?

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

OK - I'm really sorry !!
I also get 'u' -- I had a typo there ... 

But what is the complete list of kind values ?

-Sebastian


On Tuesday 19 September 2006 11:54, Scott Ransom wrote:
> > > Can anybody on a 64-bit system confirm?
> >
> > I'm on 64-bit Debian:
> >
> > In [11]: arr=N.arange(10,dtype=N.uint)
> >
> > In [12]: arr.dtype.kind
> > Out[12]: 'u'
> >
> > In [13]: arr.dtype.itemsize
> > Out[13]: 4
> >
> > In [14]: arr=N.arange(10,dtype=N.long)
> >
> > In [15]: arr.dtype.kind
> > Out[15]: 'i'
> >
> > In [16]: arr.dtype.itemsize
> > Out[16]: 8
>
> Ack!  That was on the wrong machine (32-bit Debian).  Here is the 64-bit
> version:
>
> In [2]: arr=N.arange(10,dtype=N.uint)
>
> In [3]: arr.dtype.kind
> Out[3]: 'u'
>
> In [4]: arr.dtype.itemsize
> Out[4]: 8
>
> In [5]: arr=N.arange(10,dtype=N.long)
>
> In [6]: arr.dtype.kind
> Out[6]: 'i'
>
> In [7]: arr.dtype.itemsize
> Out[7]: 8
>
> Sorry about that,
>
> Scott

Re: [Numpy-discussion] arr.dtype.kind is 'i' for dtype=unit !?

[Matthew B. <mat...@gm...>]

Hi,

> It's in the array interface specification:
>
> http://numpy.scipy.org/array_interface.shtml

I was interested in the 't' (bitfield) type - is there an example of
usage somewhere?

In [13]: dtype('t8')
---------------------------------------------------------------------------
exceptions.TypeError                                 Traceback (most
recent call last)

/home/mb312/python/<ipython console>

TypeError: data type not understood

Best,

Matthew

Re: [Numpy-discussion] arr.dtype.kind is 'i' for dtype=unit !?

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

Matthew Brett wrote:
> Hi,
>
>   
>> It's in the array interface specification:
>>
>> http://numpy.scipy.org/array_interface.shtml
>>     
>
> I was interested in the 't' (bitfield) type - is there an example of
> usage somewhere?
>   
No,  It's not implemented in NumPy.  It's just part of the array 
interface specification for completeness.

-Travis

Re: [Numpy-discussion] arr.dtype.kind is 'i' for dtype=unit !?

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

Sebastian Haase wrote:

>OK - I'm really sorry !!
>I also get 'u' -- I had a typo there ... 
>
>But what is the complete list of kind values ?
>  
>
It's in the array interface specification:

http://numpy.scipy.org/array_interface.shtml

-Travis