我有一个使用datetime.utcnow()
创建并持久存储在数据库中的python datetime
实例。
为了便于显示,我想将从数据库检索到的datetime
实例转换为使用默认本地时区的本地datetime
(即,就好像datetime
是使用datetime.now()
创建的一样)。
如何仅使用python标准库(例如,无pytz
依赖)将UTC datetime
转换为本地datetime
?
似乎一种解决方案是使用datetime.astimezone(tz)
,但是如何获得默认的本地时区呢?
发布于 2010-12-30 23:02:47
我想我弄明白了:计算从纪元开始的秒数,然后使用time.localtime转换为本地时间,然后将时间结构转换回datetime……
EPOCH_DATETIME = datetime.datetime(1970,1,1)
SECONDS_PER_DAY = 24*60*60
def utc_to_local_datetime( utc_datetime ):
delta = utc_datetime - EPOCH_DATETIME
utc_epoch = SECONDS_PER_DAY * delta.days + delta.seconds
time_struct = time.localtime( utc_epoch )
dt_args = time_struct[:6] + (delta.microseconds,)
return datetime.datetime( *dt_args )
它正确地应用夏季/冬季DST:
>>> utc_to_local_datetime( datetime.datetime(2010, 6, 6, 17, 29, 7, 730000) )
datetime.datetime(2010, 6, 6, 19, 29, 7, 730000)
>>> utc_to_local_datetime( datetime.datetime(2010, 12, 6, 17, 29, 7, 730000) )
datetime.datetime(2010, 12, 6, 18, 29, 7, 730000)
发布于 2012-11-08 18:22:27
在Python 3.3+中:
from datetime import datetime, timezone
def utc_to_local(utc_dt):
return utc_dt.replace(tzinfo=timezone.utc).astimezone(tz=None)
在Python 2/3中:
import calendar
from datetime import datetime, timedelta
def utc_to_local(utc_dt):
# get integer timestamp to avoid precision lost
timestamp = calendar.timegm(utc_dt.timetuple())
local_dt = datetime.fromtimestamp(timestamp)
assert utc_dt.resolution >= timedelta(microseconds=1)
return local_dt.replace(microsecond=utc_dt.microsecond)
使用pytz
(都是Python2/3):
import pytz
local_tz = pytz.timezone('Europe/Moscow') # use your local timezone name here
# NOTE: pytz.reference.LocalTimezone() would produce wrong result here
## You could use `tzlocal` module to get local timezone on Unix and Win32
# from tzlocal import get_localzone # $ pip install tzlocal
# # get local timezone
# local_tz = get_localzone()
def utc_to_local(utc_dt):
local_dt = utc_dt.replace(tzinfo=pytz.utc).astimezone(local_tz)
return local_tz.normalize(local_dt) # .normalize might be unnecessary
示例
def aslocaltimestr(utc_dt):
return utc_to_local(utc_dt).strftime('%Y-%m-%d %H:%M:%S.%f %Z%z')
print(aslocaltimestr(datetime(2010, 6, 6, 17, 29, 7, 730000)))
print(aslocaltimestr(datetime(2010, 12, 6, 17, 29, 7, 730000)))
print(aslocaltimestr(datetime.utcnow()))
输出
Python 3.3
2010-06-06 21:29:07.730000 MSD+0400
2010-12-06 20:29:07.730000 MSK+0300
2012-11-08 14:19:50.093745 MSK+0400
Python 2
2010-06-06 21:29:07.730000
2010-12-06 20:29:07.730000
2012-11-08 14:19:50.093911
pytz
2010-06-06 21:29:07.730000 MSD+0400
2010-12-06 20:29:07.730000 MSK+0300
2012-11-08 14:19:50.146917 MSK+0400
注意:它考虑了DST和MSK时区utc偏移量的最新变化。
我不知道非pytz解决方案是否适用于Windows。
发布于 2010-12-30 22:42:24
从Python3.9开始,您可以使用zoneinfo
模块。
首先,让我们使用utcnow()
来获得时间
>>> from datetime import datetime
>>> database_time = datetime.utcnow()
>>> database_time
datetime.datetime(2021, 9, 24, 4, 18, 27, 706532)
然后创建时区:
>>> from zoneinfo import ZoneInfo
>>> utc = ZoneInfo('UTC')
>>> localtz = ZoneInfo('localtime')
然后转换。要在时区之间转换,datetime必须知道它所在的时区,然后我们只需使用astimezone()
>>> utctime = database_time.replace(tzinfo=utc)
>>> localtime = utctime.astimezone(localtz)
>>> localtime
datetime.datetime(2021, 9, 24, 6, 18, 27, 706532, tzinfo=zoneinfo.ZoneInfo(key='localtime'))
对于Python3.6到3.8,您需要backports.zoneinfo模块:
>>> try:
>>> from zoneinfo import ZoneInfo
>>> except ImportError:
>>> from backports.zoneinfo import ZoneInfo
其余的都是一样的。
对于早于此的版本,则需要pytz
或dateutil
。datutil的工作原理类似于zoneinfo:
>>> from dateutil import tz
>>> utc = tz.gettz('UTC')
>>> localtz = tz.tzlocal()
The Conversion:
>>> utctime = now.replace(tzinfo=UTC)
>>> localtime = utctime.astimezone(localtz)
>>> localtime
datetime.datetime(2010, 12, 30, 15, 51, 22, 114668, tzinfo=tzlocal())
pytz
有一个不同的接口,这是由于Python的时区处理不能处理不明确的时间:
>>> import pytz
>>> utc = pytz.timezone('UTC')
# There is no local timezone support, you need to know your timezone
>>> localtz = pytz.timezone('Europe/Paris')
>>> utctime = utc.localize(database_time)
>>> localtime = localtz.normalize(utctime.astimezone(localtz))
>>> localtime
https://stackoverflow.com/questions/4563272
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