[Python-ideas] datetime: Support infinity

[Chris Barker]

On Thu, Jan 29, 2015 at 11:19 AM, Yawar Amin <yawar.amin at gmail.com> wrote:

> My test implementation works for me on Python 2.7, see http://repl.it/9Wz
>

cool site!

And yes, it does appear to work.

However the subclassing approach is really weird, as the infinite datetimes
have a year, month, day, etc -- that strikes me as ripe for error. That's
why I didn't subclass, but just had them e independent.

Another option would be to override just about everything...

-Chris



> Notice especially the last few assertions, where normal datetime objects
> are on the LHS.
>
> Regards,
>
> Yawar
>
> On 2015-01-29, at 2:04, Chris Barker <chris.barker at noaa.gov> wrote:
>
> On Wed, Jan 28, 2015 at 6:55 PM, Yawar Amin <yawar.amin at gmail.com> wrote:
>
>> Cool, the comparison operator logic looks very similar to mine:
>>
>> https://groups.google.com/d/msg/python-ideas/G3jeWoa6h14/ELpDLFu28QcJ
>>
>>
> Did you get it to work both ways? i.e.
>
> datetime.neg_inf < datetime.now()
>
> and
>
> datetime.now() > datetime.neg_inf
>
> I had trouble with that, because the regular datetime doesn't know how to
> compare itself to a neg_inf object.
>
>
>> I believe the ideal design is the following type hierarchy:
>>
>>     datetime_base
>>       datetime_neg_inf
>>       datetime_pos_inf
>>       datetime
>>
>> But in the interests of pragmatism, I think this one can be made to
>> work:
>>
>>     datetime
>>       datetime_neg_inf
>>       datetime_pos_inf
>>
>
> yup -- should work.
>
> and you could add class methods to the datetime object, so you could do:
>
> datetime.neg_inf()
> and
> datetime.pos_inf()
>
>
>> The
>>
> advantage to this is that we don't have to switch everything over to
>> using a new derived type--just use the normal datetime for the majority
>> of cases where we don't need inifinity dates.
>>
>
> And it could be a third part package, too. -- particularly good for
> backward compatibility.
>
> -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 at noaa.gov
>
>


-- 

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 at noaa.gov
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