解决方案
当您调用 ts2.replace(tzinfo = EST)时, tzinfo 你得到的不符合你所得到的 ts1 :
>>> ts1 datetime.datetime(2014,5,16,11,51,7,916090,tzinfo =< DstTzInfo'America / New_York'EDT-1天,20:00:00 DST>) >>> ts2 datetime.datetime(2014,5,16,11,51,30,922692,tzinfo =< DstTzInfo'America / New_York'LMT-1天,19:04:00 STD>)您最终使用LMT而不是EDT。
pytz 文档实际上注意到使用标准datetime对象的 tzinfo 参数的pytz 根本不适用于许多时区:
不幸的是,使用标准datetime 构造函数的tzinfo参数对于许多时区来说并不适用于pytz。
>>> datetime(2002,10,27,12,0,0,tzinfo = amsterdam).strftime(fmt)'2002-10-27 12:00:00 LMT + 0020'
对于没有夏令时转换的时区,如UTC:
>>> datetime(2002,10,27,12,0,0,tzinfo = pytz.utc).strftime(fmt)'2002-10-27 12:00:00 UTC + 0000'
我不知道为什么第一个工作;也许是因为当对象最初使用 tzinfo 对象构造时,实际上不需要转换任何东西。
编辑:
啊,Python 文档注意到使用 datetime.datetime.now()与 tz arg相当于:
EST.fromutc(datetime.utcnow()。replace(tzinfo = EST))这意味着你正在从UTC转换,这是安全的, pytz 。所以这就是为什么第一个工作。
I ran across an interesting situation today. Can anyone explain why the offsets for ts1 and ts2 are different? ts1 is a datetime object that is timezone-aware right off the bat. ts2 is a datetime object that starts off timezone-naive and has its tzinfo replaced. However, they end up with different offsets.
>>> from pytz import timezone >>> EST = timezone('America/New_York') >>> ts1 = datetime.datetime.now(tz=EST) >>> ts2 = datetime.datetime.now() >>> ts2 = ts2.replace(tzinfo=EST) >>> print ts1 2014-05-16 11:25:16.749748-04:00 >>> print ts2 2014-05-16 11:25:19.581710-05:00解决方案
When you call ts2.replace(tzinfo=EST), the tzinfo object you're getting doesn't match the one you get with ts1:
>>> ts1 datetime.datetime(2014, 5, 16, 11, 51, 7, 916090, tzinfo=<DstTzInfo 'America/New_York' EDT-1 day, 20:00:00 DST>) >>> ts2 datetime.datetime(2014, 5, 16, 11, 51, 30, 922692, tzinfo=<DstTzInfo 'America/New_York' LMT-1 day, 19:04:00 STD>)You end up with LMT instead of EDT.
The pytz documentation actually notes that using pytz with the tzinfo argument of standard datetime objects simply doesn't work for many timezones:
Unfortunately using the tzinfo argument of the standard datetime constructors ''does not work'' with pytz for many timezones.
>>> datetime(2002, 10, 27, 12, 0, 0, tzinfo=amsterdam).strftime(fmt) '2002-10-27 12:00:00 LMT+0020'
It is safe for timezones without daylight saving transitions though, such as UTC:
>>> datetime(2002, 10, 27, 12, 0, 0, tzinfo=pytz.utc).strftime(fmt) '2002-10-27 12:00:00 UTC+0000'
I'm not exactly sure why the first one works; perhaps because it doesn't actually have to convert anything when the object is initially constructed with the tzinfo object.
Edit:
Ah, the Python documentation notes that using datetime.datetime.now() with the tz arg is equivalent to:
EST.fromutc(datetime.utcnow().replace(tzinfo=EST))Which means you're converting from UTC, which is safe with pytz. So that's why the first one works.
更多推荐
datetime与pytz时区。不同的偏移取决于如何设置tzinfo
发布评论