ISO with timezone

[nik]

Hi,

How does one express the time in ISO format with the timezone
designator?

what I want is YYYY-MM-DDThh:mm:ss.sTZD

>From the documentation I see:
>>> from datetime import tzinfo, timedelta, datetime
>>> class TZ(tzinfo):
...     def utcoffset(self, dt): return timedelta(minutes=-399)
...
>>> datetime(2002, 12, 25, tzinfo=TZ()).isoformat(' ')
'2002-12-25 00:00:00-06:39'

and I've also figured out:
>>>datetime.datetime.fromtimestamp(time.time()).isoformat()[:-3]
'2008-01-23T11:22:54.130'

But can't figure out how to fit them together.

Thank you,
Nik