Output ISO 8601 format datetime string in UTC timezone

I hate timezone. Especially for python, since python’s timezone is not in standard library, I always need to install pytz. I know it make sense, since timezone db changes sometimes, and it make no sense to put it in python standard library. But this make life harder. Every time when I work on timezone aware datetime, it will #FML.

The formal way is name your timezone in config file, but for the case of output iso 8601 format datetime in UTC timezone, it’s not elegant to ask for this information. The tricky part is get your local timezone. Since timezone is not in system environment variable, so it’s kind of hack to let it work with small code footprint. I know I’m stupid, but let me post my solution here. If you know better solution, please let me know.

try:
    local_tz = pytz.build_tzinfo('localtime', open('/etc/localtime', 'rb'))
except:
    from .poorman_tz import LocalTimezone
    local_tz = LocalTimezone()


def isoformat(dt):
    if dt:
        return local_tz.localize(dt).replace(microsecond=0).astimezone(pytz.utc).isoformat()
    return None

The LocalTimezone is from python’s datetime document, just copy that section of code and you get this poorman’s implementation of LocalTimezone. Thanks my coworker Stan pointing me out the solution to build a timezone from /etc/localtime, also for this smart guy answer that stackoverflow thread. BTW: python’s datetime has microsecond information, I don’t need them so I replace them with 0, it makes the datetime string shorter.