python - pytz: _utcoffset has a wrong value for Iran -

correct value:

>>> pytz.timezone('asia/tehran').utcoffset(datetime(2013, 1, 1)).total_seconds()/3600.0 3.5  >>> pytz.timezone('asia/tehran').utcoffset(datetime(2013, 1, 1)).total_seconds() 12600.0 

incorrect value:

>>> pytz.timezone('asia/tehran')._utcoffset.total_seconds()/3600.0 3.433333333333333  >>> pytz.timezone('asia/tehran')._utcoffset.total_seconds() 12360.0 

i wonder if _utcoffset attribute used in utcoffset() method, why method working while attribute wrong.
looks bug anyway.
nothing changes if replace asia/tehran iran

>>> print pytz.version 2012c 

os: linux mint 15 (olivia)
using python 2.7

let's see what's going on here:

>>> tz = pytz.timezone('asia/tehran') >>> tz <dsttzinfo 'asia/tehran' lmt+3:26:00 std> 

this means timezone expressed in lmt - solar time. that's why see utcoffset of 12360 - no error here, it's calculated using different reference.

now if do:

>>> d = tz.localize(datetime(2013, 1, 1)) >>> d datetime.datetime(2013, 1, 1, 0, 0, tzinfo=<dsttzinfo 'asia/tehran' irst+3:30:00 std>) >>> d.utcoffset() datetime.timedelta(0, 12600) 

the localize method caused representation switch correct time zone used @ date , place, irst utcoffset of 12600 seconds.

and that's utcoffset method of tzinfo object - localizes given datetime object , returns it's utcoffset.

likewise if do:

>>> d = datetime.now(tz) >>> d datetime.datetime(2013, 8, 15, 20, 46, 4, 705896, tzinfo=<dsttzinfo 'asia/tehran' irdt+4:30:00 dst>) >>> d.utcoffset() datetime.timedelta(0, 16200) 

you'll datetime expressed in irdt because daylight saving time in effect in timezone.