[Python-Dev] PEP: New timestamp formats (original) (raw)

Gregory P. Smith greg at krypto.org
Fri Feb 3 22:09:22 CET 2012

Why is the PEP promoting the float type being used as the default on the new-in-3.3 APIs that were added explicitly to provide nanosecond level resolution that cannot be represented by a float?

The new APIs should default to the high precision return value (be that datetime/timedelta or decimal).

-gps

On Fri, Feb 3, 2012 at 11:32 AM, Jeffrey Yasskin <jyasskin at gmail.com> wrote:

On Fri, Feb 3, 2012 at 11:17 AM, Antoine Pitrou <solipsis at pitrou.net> wrote: > On Fri, 3 Feb 2012 11:04:14 -0800 > Jeffrey Yasskin <jyasskin at gmail.com> wrote: >> On Thu, Feb 2, 2012 at 4:59 PM, Nick Coghlan <ncoghlan at gmail.com> wrote: >> > datetime.datetime >> > >> > - real problem with the idea is that not all timestamps can be easily >> > made absolute (e.g. some APIs may return "time since system started" >> > or "time since process started") >> >> I think this is an argument for returning the appropriate one of >> datetime or timedelta from all of these functions: users need to keep >> track of whether they've got an absolute time, or an offset from an >> unspecified starting point, and that's a type-like distinction. > > Keep in mind timedelta has a microsecond resolution. The use cases > meant for the PEP imply nanosecond resolution (POSIX' clockgettime(), > for example).

Yes, I think someone had noted that datetime and timedelta would need to be extended to support nanosecond resolution. >> A plain number of seconds is superficially simpler, but it forces more >> complexity onto the user, who has to track what that number >> represents. > > If all you are doing is comparing timestamps (which I guess is most of > what people do with e.g. stmtime), a number is fine. Sure. I don't think the argument for datetime is totally convincing, just that it's stronger than the PEP currently presents. > If you want the current time and date in a high-level form, you can > already use datetime.now() or datetime.utcnow() (which "only" has > microsecond resolution as well :-)). We don't need another way to spell > it. Whoops, yes, there's no need to extend time() to return a datetime.

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