STD offset for pytz timezones

Question

i want to add UTC offset to timezone list from tz database, like: * (UTC +0) Europe/London

For list of timezones i use pytz.common_timezones, but cant retrieve STD utcoffset for timezone, because all methods on timezone object requires dt object, moment of time, when to calculate offset.

It's posible to get STD offset from pytz timezone object without manipulation with specific dates?

Thanks!

Answer 1

The pytz tzinfo objects contain the UTC transition times which mark the boundary between STD and DST. However, accessing this information requires dipping into their private attributes -- in particular, tzone._utc_transition_times, tzone._transition_info. So what follows is fragile -- pytz does not guarantee you can access the same information the same way in future versions.

Nevertheless, at least for pytz version 2010b, using the attributes above, you can find a date in the most recent period which was in STD. You can then use std_date.strftime('%z') to print the offset.

import pytz
import datetime as DT

NOW = DT.datetime.now()
ZERO = DT.timedelta(0)

for tname in pytz.common_timezones:
    tzone = pytz.timezone(tname)
    std_date = None
    try:
        for utcdate, info in zip(
                tzone._utc_transition_times, tzone._transition_info):
            utcoffset, dstoffset, tzname = info
            if dstoffset == ZERO:
                std_date = utcdate
            if utcdate > NOW:
                break
    except AttributeError:
        std_date = NOW
    std_date = tzone.localize(std_date)    
    print('{n} UTC{z}'.format(n=tname, z=std_date.strftime('%z')))

prints

Africa/Abidjan UTC+0000
Africa/Accra UTC+0000
Africa/Addis_Ababa UTC+0235
Africa/Algiers UTC+0000
Africa/Asmara UTC+0235
Africa/Bamako UTC+0000
Africa/Bangui UTC+0114
Africa/Banjul UTC+0000
...