[Python-Dev] datetime nanosecond support (ctd?) (original) (raw)

Guido van Rossum guido at python.org
Wed Dec 17 01:17:20 CET 2014

"Nothing looks quite right" is a common phenomenon when you're constrained by backward compatibility. The perfect solution would throw away compatibility, but that has its own downsides. So just go for what looks the least wrong.

On Tue, Dec 16, 2014 at 3:28 PM, Matthieu Bec <mbec at gmto.org> wrote:

Maybe what I meant with `nothing looks quite right': seconds as float, microseconds as float, nanosecond as 0..999, nanoseconds as 0..999999999 with mandatory keyword that precludes microseconds - all can be made to work, none seems completely satisfying. In fact, I don't really have a use for it from python - but something would be needed in C for the implementation of datetime.fromtimespec and time.fromtimespec that calls the constructor PyObjectCallCallFunction(clas,"...",...) - can this happen and remain hidden from the python layer? Regards, Matthieu

On 12/16/14 12:45 PM, Alexander Belopolsky wrote:

On Tue, Dec 16, 2014 at 12:10 PM, matthieu bec <mbec at gmto.org_ _<mailto:mbec at gmto.org>> wrote: I wonder if the datetime module is really the right location, that has constructor(year, month, day, ..., second, microsecond) - with 0<ms<999999, no millis. adding 0<ns<999 would seem quite ugly, in fact nothing looks quite right.

We can make nanosecond a keyword-only argument, so that time(1, 2, 3, nanosecond=123456789) -> 01:02:03.123456789 and time(1, 2, 3, 4, nanosecond=123456789) -> error Users will probably be encouraged to avoid positional form when specifying time to subsecond precision. I would say time(1, 2, 3, microsecond=4) is clearer than time(1, 2, 3, 4) anyways. Another option is to allow float for the "second" argument: time(1, 2, 3.123456789) -> 01:02:03.123456789

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