[Datetime-SIG] pytz vs. PEP 495 Was: PEP-431/495

[ISAAC J SCHWABACHER]

[ijs]
> > > I *really* hope the answer to this one is, "don't do that".

[Alexander Belopolsky]
> > That's not an option because people already *do* [1] that and they won't stop.
> > Neither they will stop using datetime.combine() [2] or datetime.replace() [3]
> > or tolerate if those methods start raising exceptions.

[Ethan Furman]
> If the default is True (or False), then this won't be a problem.  It will only be None when explicitly asked for.
>
> `time` can just store the flag, and when it is combined with a date the flag should be checked and if None and the resulting datetime doesn't exist or is ambiguous an exception can be raised.

A time with a non-constant-offset tzinfo is always ambiguous, and can have an arbitrary number of possible offsets. There are several time zones with at least three possible offsets for a given time in the last 10 years. How on earth do you define the meaning of a time with a non-constant tzinfo attached? Or does it only mean something when it's recombined with a date?

ijs