[Numpy-discussion] float('inf') // 1 = ?
Sebastian Berg
sebastian at sipsolutions.net
Thu Sep 18 13:13:58 EDT 2014
On Thu, 2014-09-18 at 18:55 +0200, Petr Viktorin wrote:
> Sorry for the lack of subject before.
>
> On Thu, Sep 18, 2014 at 6:48 PM, Benjamin Root <ben.root at ou.edu> wrote:
> > My vote is that NumPy is correct here. I see no reason why
> >>>> float('inf') / 1
> > and
> >>>> float('inf') // 1
> >
Didn't read python ideas I have to admit (at least not enough to see
many arguments). My biggest argument is that numpy does exactly this:
>>> import math
>>> math.floor(float('inf')/1)
Maybe I am naive thinking that floordivide is basically a divide+floor
operation, but arguing for NaN seems half arsed to me on first sight.
Either it is `inf` and the equivalence Benjamin Root noted holds or you
make it an error. NaN is not reasonable for an error return *especially*
not for the standard lib (it *might* be for numpy).
- Sebastian
> > should return different results.
>
> I recommend reading the python-ideas thread; there are some arguments
> for both sides.
>
> > On Thu, Sep 18, 2014 at 12:31 PM, Petr Viktorin <encukou at gmail.com> wrote:
> >>
> >> Hello,
> >> Over at Python-ideas, there is a thread [0] about the following
> >> discrepancy:
> >>
> >> >>> numpy.array(float('inf')) // 1
> >> inf
> >> >>> float('inf') // 1
> >> nan
> >>
> >> There are reasons for either result, but I believe it would be very
> >> nice if either Python or Numpy changed, so they would give the same
> >> value.
> >> If any of you have reasons to defend Numpy's (or Python's) choice, or
> >> otherwise want to chime in, please post there.
> >>
> >> Thanks,
> >> Petr Viktorin
> >>
> >>
> >> [0]
> >> https://mail.python.org/pipermail/python-ideas/2014-September/029365.html
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