[Pandas-dev] Datetime (with timezone?) as extension array?

[Tom Augspurger]

Agreed that all our internal extension arrays should be real EAs for the
0.24.0 release.

My plan has been SparseArray, then PeriodArray, then DatetimeTZArray. I'll
see what I can prototype before the meeting tomorrow

Tom

On Tue, Sep 25, 2018 at 12:41 PM Joris Van den Bossche <
jorisvandenbossche at gmail.com> wrote:

> 2018-08-14 17:32 GMT+02:00 Brock Mendel <jbrockmendel at gmail.com>:
>
>> `DatetimeArray` is close to ready if you want to bring it over the finish
>> line.  Pretty much all that has to be done is having `DatetimeArrayMixin`
>> subclass `ExtensionArray` (and, uh, implement the relevant EA methods).  If
>> no one else picks this up, my current plan is to do this _after_ updating
>> all of the relevant arithmetic tests to test DatetimeArrayMixin.
>>
>> What's the status of this?  Asking because I think having a working EA
> DatetimeArray implementation is important for a 0.24.0 release, and I can
> imagine it will still take quite some discussion and would be good to have
> it in master for a while.
>
> It's a hard to really steer this since it is volunteer based (and
> certainly because I currently don't have the time to do it myself), but to
> the extent possible, it would be good if we could try to prioritize it a
> bit.
>
> Joris
>
>
>
>> > The unclear part is what `Series[datetime_with_tz].values` should be.
>>
>> I thought the conclusion was that `.values` should be non-lossy, in which
>> case it would have to be the EA.  My preference would be for the EA to be
>> returned for non-tz datetime64[ns] Series too.
>>
>> For that matter, I'd like it if `Series.values` _always_ returned an EA,
>> but we're not there yet.
>>
>>
>> On Tue, Aug 14, 2018 at 4:13 AM, Tom Augspurger <
>> tom.augspurger88 at gmail.com> wrote:
>>
>>> The discussion on datetime with timezone has been a bit scattered. I
>>> don't think there's a single issue with everyone's thoughts.
>>>
>>> There will be a DatetimeWithTZ array that implements the EA interface.
>>> Anywhere we're internally using a DatetimeIndex as a
>>> container for datetimes with timezones will use the new EA.
>>>
>>> The unclear part is what `Series[datetime_with_tz].values` should be.
>>> Currently, we convert to UTC, strip the timezone, and return
>>> a datetime64[ns] ndarray. Changing that would be disruptive, jarringly
>>> different from `Series[datetime].values` (no tz) and of little
>>> value I think.
>>>
>>> Tom
>>>
>>> On Tue, Aug 14, 2018 at 4:07 AM Pietro Battiston <me at pietrobattiston.it>
>>> wrote:
>>>
>>>> Hi all,
>>>>
>>>> I assumed that Datetime (with timezone, or maybe in general?) was also
>>>> planned to follow the extension array interface, which is related to
>>>> issue https://github.com/pandas-dev/pandas/issues/19041 , to the
>>>> annoying fact that datetimeindexwithtz._values returns the index
>>>> itself, and also to the fact that
>>>> https://pandas.pydata.org/pandas-docs/stable/extending.html
>>>> currently states "Pandas itself uses the extension system for some
>>>> types that aren’t built into NumPy (categorical, period, interval,
>>>> datetime with timezone).", which is false.
>>>>
>>>> ... but I didn't find an issue for this? Did I miss it? Should I create
>>>> it? Or was there a decision to leave datetimeindextz as it is, maybe
>>>> for better compatibility with numpy?
>>>>
>>>> Pietro
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>>>
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>>
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