[python] How to get an isoformat datetime string including the default timezone?

I need to produce a time string that matches the iso format yyyy-mm-ddThh:mm:ss.ssssss-ZO:NE. The now() and utcnow() class methods almost do what I want.

>>> import datetime
>>> #time adjusted for current timezone
>>> datetime.datetime.now().isoformat()
'2010-08-03T03:00:00.000000'
>>> #unadjusted UTC time
>>> datetime.datetime.utcnow().isoformat()
'2010-08-03T10:00:00.000000'
>>>
>>> #How can I do this?
>>> datetime.datetime.magic()
'2010-08-03T10:00:00.000000-07:00'

With arrow:

>>> import arrow
>>> arrow.now().isoformat()
'2015-04-17T06:36:49.463207-05:00'
>>> arrow.utcnow().isoformat()
'2015-04-17T11:37:17.042330+00:00'

Nine years later. If you know your time zone. I like the T between date and time. And if you don't want microseconds.

Python <= 3.8

pip3 install pytz  # needed!

python3
>>> import datetime
>>> import pytz
>>> datetime.datetime.now(pytz.timezone('Europe/Berlin')).isoformat('T', 'seconds')
'2020-11-09T18:23:28+01:00'

Tested on Ubuntu 18.04 and Python 3.6.9.

Python >= 3.9

pip3 install tzdata  # only on Windows needed!

py -3
>>> import datetime
>>> import zoneinfo
>>> datetime.datetime.now(zoneinfo.ZoneInfo('Europe/Berlin')).isoformat('T', 'seconds')
'2020-11-09T18:39:36+01:00'

Tested on Windows 10 and Python 3.9.0.

You need to make your datetime objects timezone aware. from the datetime docs:

There are two kinds of date and time objects: “naive” and “aware”. This distinction refers to whether the object has any notion of time zone, daylight saving time, or other kind of algorithmic or political time adjustment. Whether a naive datetime object represents Coordinated Universal Time (UTC), local time, or time in some other timezone is purely up to the program, just like it’s up to the program whether a particular number represents metres, miles, or mass. Naive datetime objects are easy to understand and to work with, at the cost of ignoring some aspects of reality.

When you have an aware datetime object, you can use isoformat() and get the output you need.

To make your datetime objects aware, you'll need to subclass tzinfo, like the second example in here, or simpler - use a package that does it for you, like pytz or python-dateutil

Using pytz, this would look like:

import datetime, pytz
datetime.datetime.now(pytz.timezone('US/Central')).isoformat()

You can also control the output format, if you use strftime with the '%z' format directive like

datetime.datetime.now(pytz.timezone('US/Central')).strftime('%Y-%m-%dT%H:%M:%S.%f%z')

You can do it in Python 2.7+ with python-dateutil (which is insalled on Mac by default):

>>> from datetime import datetime
>>> from dateutil.tz import tzlocal
>>> datetime.now(tzlocal()).isoformat()
'2016-10-22T12:45:45.353489-03:00'

Or you if you want to convert from an existed stored string:

>>> from datetime import datetime
>>> from dateutil.tz import tzlocal
>>> from dateutil.parser import parse
>>> parse("2016-10-21T16:33:27.696173").replace(tzinfo=tzlocal()).isoformat()
'2016-10-21T16:33:27.696173-03:00' <-- Atlantic Daylight Time (ADT) 
>>> parse("2016-01-21T16:33:27.696173").replace(tzinfo=tzlocal()).isoformat()
'2016-01-21T16:33:27.696173-04:00' <-- Atlantic Standard Time (AST)

Something like the following example. Note I'm in Eastern Australia (UTC + 10 hours at the moment).

>>> import datetime
>>> dtnow = datetime.datetime.now();dtutcnow = datetime.datetime.utcnow()
>>> dtnow
datetime.datetime(2010, 8, 4, 9, 33, 9, 890000)
>>> dtutcnow
datetime.datetime(2010, 8, 3, 23, 33, 9, 890000)
>>> delta = dtnow - dtutcnow
>>> delta
datetime.timedelta(0, 36000)
>>> hh,mm = divmod((delta.days * 24*60*60 + delta.seconds + 30) // 60, 60)
>>> hh,mm
(10, 0)
>>> "%s%+02d:%02d" % (dtnow.isoformat(), hh, mm)
'2010-08-04T09:33:09.890000+10:00'
>>>