[Python-Dev] Draft PEP for time zone support.

Nick Coghlan ncoghlan at gmail.com
Wed Dec 12 04:14:23 CET 2012

On Wed, Dec 12, 2012 at 12:58 PM, Barry Warsaw <barry at python.org> wrote:

> On Dec 11, 2012, at 04:23 PM, Lennart Regebro wrote:
> >A new ``is_dst`` parameter is added to several of the `tzinfo` methods to
> >handle time ambiguity during DST changeovers.
> >``None`` will raise an ``AmbiguousTimeError`` exception if the time
> specified
> >was during a DST change over. It will also raise a
> ``NonExistentTimeError``
> >if a time is specified during the "missing time" in a change to DST.
> I think None should be the default.

That's a backwards compatibility risk, though - many applications are
likely coping just fine with the slightly corrupted time values, but would
fall over if an exception was raised instead. The default should probably
be chosen so that the single argument form of these calls continues to
behave the same in 3.4 as it does in 3.3, emitting a DeprecationWarning to
say that the default behaviour is going to change in 3.5 (so the *actual*
default would be sentinel value, in order to tell the difference between an
explicit True being passed and relying on the default behaviour).


Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
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