使用 Python 找出当前时区是否处于夏令时
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Use Python to find out if a timezone currently in daylight savings time
提问by Joey Mason
We have a server that runs on GMT time. I need to write a Python script that determines if it's currently (at this very second) Daylight Savings Time (DST) in Los Angeles, CA. How can I accomplish this? I took a look at pytz and time, but I can't figure it out. I realize that I could create some logic such as comparing the current time in LA to GMT time, but it would be a lot cleaner if I could use a standard library instead.
我们有一个在 GMT 时间运行的服务器。我需要编写一个 Python 脚本来确定它是否在加利福尼亚州洛杉矶当前（在这一秒）夏令时 (DST)。我怎样才能做到这一点？我看了一下pytz和时间，但我想不通。我意识到我可以创建一些逻辑，例如将 LA 的当前时间与 GMT 时间进行比较，但是如果我可以使用标准库来代替它会更清晰。
Thanks
谢谢
Edit: Here's some sample code of me setting up the timezone:
编辑：这是我设置时区的一些示例代码：
from pytz import timezone
import pytz
from datetime import datetime, timedelta
tz = timezone('America/Los_Angeles')
// Instantiate a datetime object using tz?
Edit: Here's a snippet of code that will work. It's not elegant, which is why I'm asking if there's a library or something that is made for this. Maybe like a is_dst() function.
编辑：这是一段可以工作的代码。这并不优雅，这就是为什么我要问是否有图书馆或为此专门制作的东西。也许就像一个 is_dst() 函数。
utc = timezone("UTC")
now = utc.localize(datetime.utcnow())
los_angeles_tz = timezone('America/Los_Angeles')
los_angeles_time = now.astimezone(los_angeles_tz)
delta = los_angeles_time.utcoffset()
dstDelta = timedelta(hours=-8)
is_dst = (delta == dstDelta)
回答by Matt Johnson-Pint
import pytz
from datetime import datetime, timedelta
def is_dst(zonename):
tz = pytz.timezone(zonename)
now = pytz.utc.localize(datetime.utcnow())
return now.astimezone(tz).dst() != timedelta(0)
Usage:
用法：
>>> is_dst("America/Los_Angeles")
False
>>> is_dst("America/Sao_Paulo")
True
回答by jfs
from datetime import datetime
import pytz
isdst_now_in = lambda zonename: bool(datetime.now(pytz.timezone(zonename)).dst())
Example:
例子：
>>> isdst_now_in("America/Los_Angeles") # 2014-10-27 12:32:07 PDT-0700
True
>>> isdst_now_in("Australia/Melbourne") # 2014-10-28 06:32:07 AEDT+1100
True
Here's stdlib-only version on Unix using time.tzset()function:
这是 Unix 上使用time.tzset()function的 stdlib-only 版本：
import os
import time
from contextlib import contextmanager
@contextmanager
def local_timezone(zonename):
#NOTE: it manipulates global state
oldname = os.environ.get('TZ')
try:
os.environ['TZ'] = zonename
time.tzset()
yield
finally:
if oldname is None:
del os.environ['TZ']
else:
os.environ['TZ'] = oldname
time.tzset()
def time_isdst_now_in(zonename):
with local_timezone(zonename):
return time.localtime().tm_isdst > 0
The usage is the same:
用法是一样的：
>>> time_isdst_now_in('Europe/London') # 2014-04-17 18:42:11 BST+0100
True
Note: time.daylightis not used due to issues in some edge cases.
注意：time.daylight由于某些边缘情况下的问题，不使用。
