On Wed, Feb 17, 2010 at 3:48 PM, David Perlman <dperl...@wisc.edu> wrote: > Surely there is a way to simply print out the local time, date and time zone > without needing to write your own class... I can't believe this is the only > way... > > Here's why I don't believe it. Both the datetime and time modules provide > both functions for returning the current local time, and the current utc > time. So, assuming that those functions are trustworthy, it *must* be true > that the OS always knows the current offset from utc time. So why is there > no straightforward way to get that offset in python? I mean, I can do this:
time.timezone gives the offset for standard time. Kent > >>>> datetime.datetime.now()-datetime.datetime.utcnow() > datetime.timedelta(-1, 64799, 999987) > > But then, of course, it's off by a few fractions of a microsecond. This > works: > >>>> time.localtime()[3]-time.gmtime()[3] > -6 > > But doesn't that seem like a ridiculous hack, well outside of the spirit of > the zen of python? Shouldn't there be one obvious right way to do this? > > Yes, I know that as William sent, the documentation points out that the > rules the world over are complicated and irrational. Nonetheless, it is > implicit in the existing definitions that the system *knows* the current > offset, even if it doesn't know the whole set of rules... > > > On Feb 17, 2010, at 2:26 PM, Kent Johnson wrote: > >> On Wed, Feb 17, 2010 at 3:12 PM, David Perlman <dperl...@wisc.edu> wrote: >>> >>> Yeah, I got this part. The thing that's hanging me up is that there >>> doesn't >>> seem to be any way to get a tzinfo instance that contains the current >>> local >>> time zone information. You can do time.timezone to get the seconds from >>> UTC, but there doesn't seem to be any way to convert that into a tzinfo! >>> I >>> would be perfectly satisfied with this: >>> >>> tz=offset_to_tzinfo(time.timezone) # or whatever >>> aware_now=datetime.datetime.now(tz) >>> print aware_now.isoformat() >>> >>> I'm pretty sure that would give me what I want, but there doesn't seem to >>> be >>> any way to do step one without subclassing tzinfo. This makes me feel >>> like >>> I MUST be missing something obvious, because it shouldn't require so much >>> coding just to find out what the current local time and timezone is! >> >> The docs make it clear that you do have to subclass tzinfo, that no >> implementations are provided. >> It sounds like you want the LocalTimezone class in the examples at the >> bottom of this section - "A class capturing the platform's idea of >> local time": >> http://docs.python.org/library/datetime.html#tzinfo-objects >> >> Kent > > -- > -dave---------------------------------------------------------------- > "Pseudo-colored pictures of a person's brain lighting up are > undoubtedly more persuasive than a pattern of squiggles produced by a > polygraph. That could be a big problem if the goal is to get to the > truth." -Dr. Steven Hyman, Harvard > > > > _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
