[Numpy-discussion] Should bool_ subclass int?

Timothy Hochberg tim.hochberg@ieee....
Sat Jul 7 11:10:54 CDT 2007


On 7/7/07, Travis Oliphant <oliphant.travis@ieee.org> wrote:
>
>
> >
> >
> > On 7/6/07, *Travis Oliphant* <oliphant.travis@ieee.org
> > <mailto:oliphant.travis@ieee.org>> wrote:
> >
> >     Timothy Hochberg wrote:
> >     >
> >     > I'm working on getting some old code working with numpy and I
> >     noticed
> >     > that bool_ is not a subclass of int. Given that python's bool
> >     > subclasses into and that the other scalar types are subclasses of
> >     > their respective counterparts it seems at first glance that
> >     > numpy.bool_ should subclass python's bool, which in turn
> subclasses
> >     > int. Or am I missing something here?
> >     The reason it is not, is because it is not binary compatible with
> >     Python's integer.   The numpy bool_ is always only 8-bits while the
> >     Python integer is 32-bits or 64-bits.
> >
> >     This could be changed I suspect, but then it would break the
> >     relationship between scalars and their array counterparts
> >
> >
> > Do you have and idea off the top of your head head how painful this
> > would be from an implementation standpoint. And is there a theoretical
> > reason that it is important that the scalar and array implementations
> > match? I would think that, conceptually, they are all 1-bit integers,
> > and it seems that the 8-bit, versus 32- or 64-bits is just an
> > implementation detail.
> It would probably take about 2-3 hours to make the change and about 3
> more hours to fix the problems that were not anticipated.    Basically,
> we would have to special-case the bool like we do the unicode scalar
> (which also doesn't necessarily match the array-based representation but
> instead follows the Python implementation).
>
> I guess I don't really see a problem in switching just the numpy.bool_
> scalar to be a sub-class of the Python bool type and adjusting the code
> to make the switch when creating a scalar.



Thanks for info. I'll put this on my list of things to look into, although
it may take me a few weeks to get around to it, depending on how busy next
week is.  I don't see this as urgent, but it seems like a good change to
make going forward.


-- 
.  __
.   |-\
.
.  tim.hochberg@ieee.org
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