[Numpy-discussion] What is a numpy.long type?

Sebastian Berg sebastian@sipsolutions....
Fri Aug 23 10:11:56 CDT 2013


On Fri, 2013-08-23 at 07:59 -0700, Chris Barker - NOAA Federal wrote:
> On Aug 22, 2013, at 11:57 PM, David Cournapeau <cournape@gmail.com>
> wrote:
> 
> 
<snip>
> 
> > arch -32 python -c "import numpy as np; print np.dtype(np.int);
> > print np.dtype(np.long)"
> > int32
> > int64
> 
> 
> So this is giving us a 64 bit int--not a bad compromise, but not a
> python long--I've got to wonder why the alias is there at all.
> 
It is there because you can't remove it :).
> 
> > arch -64 python -c "import numpy as np; print np.dtype(np.int);
> > print np.dtype(np.long)"
> > int64
> > int64
> > 
> > 
> Same thing on 64 bit.
> 
> 
> So while np.long is an alias to python long--it apparently is
> translated internally as 64 bit -- everywhere?
> 
Not sure how a python long is translated...
> 
> So apparently there is no way to get a "platform long". ( or, for that
> matter, a platform anything else, it's just that there is more
> consistancy among common platforms for the others)
> 
An np.int_ is a platform long, since the python ints are C longs. It is
a bit weird naming, but it is transparent. Check
http://docs.scipy.org/doc/numpy-dev/reference/arrays.scalars.html#built-in-scalar-types

you got everything platform dependend there really. `intc` is an int,
`int_` is a long, and you got `longlong`, as well as `intp` which is an
ssize_t, etc.

- Sebastian

> 
> -Chris
> 
> 
> 
> 
> > All this is on python 2.7, I am not sure how/if that changes on
> > python 3 (that consolidated python int/long).
> > 
> > 
> > David
> >         
> >         -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
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