Re: [Datetime-SIG] Calendar vs timespan calculations...
On 07/30/2015 03:10 PM, Chris Barker wrote:
By the way -- which __add__ actually does the implementation? datetime's or timedelta's ?
class timedelta: def __add__(self, other): if isinstance(other, timedelta): # for CPython compatibility, we cannot use # our __class__ here, but need a real timedelta return timedelta(self._days + other._days, self._seconds + other._seconds, self._microseconds + other._microseconds) return NotImplemented timedelta only adds directly to other timedeltas; so datetime is doing the actual addition. -- ~Ethan~
On Thu, Jul 30, 2015 at 3:24 PM, Ethan Furman <ethan@stoneleaf.us> wrote:
By the way -- which __add__ actually does the implementation? datetime's
or timedelta's ?
class timedelta:
def __add__(self, other): if isinstance(other, timedelta): # for CPython compatibility, we cannot use # our __class__ here, but need a real timedelta return timedelta(self._days + other._days, self._seconds + other._seconds, self._microseconds + other._microseconds) return NotImplemented
timedelta only adds directly to other timedeltas; so datetime is doing the actual addition.
great, thanks -- so timedelta knows nothing of datetimes at all, it seems -- nice! And you are quite right -- what we need a datetime with a different __add__ (and a few others, I suppose) And it could be pretty darn backward compatible -- it would behave exactly the same for naive datetimes, and, I think, any time zone without a DST, and even any timezone when the DST boundary isn't crossed. I'm thinking its "as simple" as: - convert to utc - convert to a timedelta from year 1 - do the addition - convert back to a utc datetime - convert back to the tzinfo's timezone Or is there more to it than that that I'm missing? -Chris
-- ~Ethan~ _______________________________________________ Datetime-SIG mailing list Datetime-SIG@python.org https://mail.python.org/mailman/listinfo/datetime-sig The PSF Code of Conduct applies to this mailing list: https://www.python.org/psf/codeofconduct/
-- 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@noaa.gov
participants (2)
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Chris Barker -
Ethan Furman