[Python-Dev] Draft PEP for time zone support. (original) (raw)

Barry Warsaw barry at python.org
Wed Dec 12 03:50:49 CET 2012

Great work, Lennart. I really like this PEP. Feedback follows (I haven't yet read the rest of the messages in this thread ;).

On Dec 11, 2012, at 04:23 PM, Lennart Regebro wrote:

This PEP proposes to add these isdst parameters to the relevant methods of the datetime API, and therefore add this functionality directly to datetime. This is likely the hardest part of this PEP as this involves updating the

Oops, something got cut off there.

The new timezone-module ---------------------------

The public API of the new timezone-module contains one new class, one new function and one new exception.

Why add a new module instead of putting all this into the existing datetime module, either directly or as a submodule? Seems like the obvious place to put it instead of claiming another top-level module name.

* New class: DstTzInfo

This class provides a concrete implementation of the zoneinfo base class that implements DST support.

Is this a subclass of datetime.tzinfo?

* New function :gettimezone(name=None, db=None)

This function takes a name string that must be a string specifying a valid zoneinfo timezone, ie "US/Eastern", "Europe/Warsaw" or "Etc/GMT+11". If not given, the local timezone will be looked up. If an invalid zone name are given, or the local timezone can not be retrieved, the function raises UnknownTimeZoneError. The function also takes an optional path to the location of the zoneinfo database which should be used. If not specified, the function will check if the timezonedata module is installed, and then use that location or otherwise use the database in /usr/share/zoneinfo.

I'm bikeshedding, but can we find a better name than db for the second argument? Something that makes it obvious we're looking for file system path?

* New Exception: UnknownTimeZoneError

I'd really like to see a TimeZoneError base class from which all these new exceptions inherit.

A new isdst parameter is added to several of the tzinfo methods to handle time ambiguity during DST changeovers.

* tzinfo.utcoffset(self, dt, isdst=True)

I lied a little bit - I did skim the other messages, so I'll reserve comment on the default value of is_dst for follow ups.

* AmbiguousTimeError

* NonExistentTimeError

I'm not positive we need separate exceptions here, but I guess it can't hurt, and with the base class idea above, we can catch both either explicitly, or by catching the base class.

The timezonedata-package -----------------------------

Just to be clear, this doesn't expose any new modules, right?

Cheers, -Barry -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 836 bytes Desc: not available URL: <http://mail.python.org/pipermail/python-dev/attachments/20121211/8c9f9c4a/attachment.pgp>

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