[Python-ideas] Floating point contexts in Python core

[Guido van Rossum]

On Thu, Oct 11, 2012 at 11:42 AM, Oscar Benjamin
<oscar.j.benjamin at gmail.com> wrote:
> On 11 October 2012 17:05, Stephen J. Turnbull <stephen at xemacs.org> wrote:
>> Steven D'Aprano writes:
>>
>>  > I would gladly give up a small amount of speed for better control
>>  > over floats, such as whether 1/0.0 raised an exception or
>>  > returned infinity.
>>
>> Isn't that what the fpectl module is supposed to buy, albeit much less
>> pleasantly than Decimal contexts do?
>
> But the fpectl module IIUC wouldn't work for 1 / 0. Since Python has
> managed to unify integer/float division now it would be a shame to
> introduce any new reasons to bring in superfluous .0s again:
>
> with context(zero_division='infinity'):
>     x = 1 / 0.0  # float('inf')
>     y = 1 / 0  # I'd like to see float('inf') here as well
>
> I've spent 4 hours this week in computer labs with students using
> Python 2.7 as an introduction to scientific programming. A significant
> portion of that time was spent explaining the int/float division
> problem. They all get the issue now but not all of them understand
> that it is specifically about division: many are putting .0s
> everywhere. I expect it to be easier when we use Python 3 and I can
> simply explain that there are two types of division with two different
> operators.

You could have just told them to "from __future__ import division"

-- 
--Guido van Rossum (python.org/~guido)