[Numpy-discussion] Should bool_ subclass int?
tim.hochberg at ieee.org
Sat Jul 7 12:10:54 EDT 2007
On 7/7/07, Travis Oliphant <oliphant.travis at ieee.org> wrote:
> > On 7/6/07, *Travis Oliphant* <oliphant.travis at ieee.org
> > <mailto:oliphant.travis at 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
> > > 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 at ieee.org
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