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import os
from datetime import datetime
from typing import Tuple
import pytz
tzlocal = None
try:
import tzlocal # Maybe we can use the tzlocal module to get a safe timezone
except ImportError:
pass
# Set the local timezone for DateTime conversions. Note in most cases we want to use either UTC or the server
# timezone, but if someone insists on using the local timezone we will try to convert. The problem is we
# never have anything but an epoch timestamp returned from ClickHouse, so attempts to convert times when the
# local timezone is "DST" aware (like 'CEST' vs 'CET') will be wrong approximately half the time
local_tz: pytz.timezone
local_tz_dst_safe: bool = False
def normalize_timezone(timezone: pytz.timezone) -> Tuple[pytz.timezone, bool]:
if timezone.tzname(None) in ('UTC', 'GMT', 'Universal', 'GMT-0', 'Zulu', 'Greenwich'):
return pytz.UTC, True
if timezone.tzname(None) in pytz.common_timezones:
return timezone, True
if tzlocal is not None: # Maybe we can use the tzlocal module to get a safe timezone
local_name = tzlocal.get_localzone_name()
if local_name in pytz.common_timezones:
return pytz.timezone(local_name), True
return timezone, False
try:
local_tz = pytz.timezone(os.environ.get('TZ', ''))
except pytz.UnknownTimeZoneError:
local_tz = datetime.now().astimezone().tzinfo
local_tz, local_tz_dst_safe = normalize_timezone(local_tz)
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