[Datetime-SIG] PEP-0500 (Alternative datetime arithmetic) Was: PEP 495 ... is ready ...

Alexander Belopolsky alexander.belopolsky at gmail.com
Tue Aug 18 17:55:30 CEST 2015

On Tue, Aug 18, 2015 at 11:36 AM, Tim Peters <tim.peters at gmail.com> wrote:
> [Ethan Furman]
>>> Having briefly read PEP 500 it seems to me the primary use case is the DST
>>> transition; I can easily imagine experiments, studies, laboratory processes,
>>> etc., that need to be aware of how many hours have/will have passed, and
>>> being off by that one hour (or 30 minutes, or whatever) is simply not
>>> acceptable.
> [Guido]
>> Yes, but there are other options. PEP 500 allows way more freedom than is
>> needed.
> Another approach to consider:  _nothing_ is needed beyond PEP 495.

+1 - Implementation of PEP 495 in stdlib will keep tzinfo providers
busy for quite some time.  Hopefully, we will be able to get the
implementation in early enough in 3.6 cycle to give them an
opportunity to release concurrently with CPython.

My main concern with the alternative arithmetic is that while it may
be a desired feature for many users, it may complicate implementation
of timezone conversions and the inner working of concrete tzinfo
subclasses.  I think we should give tzinfo providers a chance to
digest PEP 495 before we hit them with PEP 500.

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