[Python-Dev] datetime +/- scalars (int, long, float)? (original) (raw)

Jason Orendorff jason@jorendorff.com
Thu, 7 Mar 2002 00:07:33 -0600

Guido van Rossum wrote:

Maybe we need yet another datetime type that measures "wall clock time"???

Gosh, time computations are full of surprises, even of you disregard the Julian calendar and leap seconds. :-(

It's good to hear you say that. Your opinion earlier -- which I wanted to agree with, but couldn't see how -- seemed to be "This is so EASY, why can't anybody just get it done the way I want??!"

:)

Elsewhere, Guido van Rossum wrote:

I'm very tempted to put all the smarts in conversions though: you can take a naive datetime object, interpret it in a particular timezone using a given DST ruleset (local time and UTC being two common cases) and convert it to a timestamp, which has different semantics, but can be converted back to naive time by interpreting according to some timezone.

Okay: Dumb objects, smart conversions.

I like this a lot. If the conversions are even minimally flexible, better timezone support can be added later. Maybe even calendars.

timestamp <---timezone/calendar-aware conversion---> datetime (no TZ or DST) (broken-down; with TZ; maybe not DST)

Casual users would only ever see (or care about) the datetime type and its year/month/day/etc. fields. By default, the broken-down time is determined using localtime().

Sometimes timestamps are appropriate, sometimes datetimes. They serve different programming goals. Both are small in terms of storage; each supports a different sort of arithmetic. Both have fast cmp operations.

For simplicity, the timestamp type could just be "float" (the type returned by time.time()). Or it could be something nicer that has (naively) broken-down fields of its own.

I've got pseudocode if anyone is interested. :|

Jason Orendorff http://www.jorendorff.com/