Get tz offset from string

问题

I have a date which is in local time:

date: "2013-12-02 22:00:00"

and another value the tz:

timezone_offset: "GMT-0800"

If I : dateutil.parser.parse(date).isoformat() I will get:

"2013-12-02T22:00:00+0000"

I want to implement the date in ISO format with the tz info and get a result of:

"2013-12-02T22:00:00-0800"

Something close to: parse(date,tzinfos=??).isoformat() ? How can I get the tzinfo from the string timezone_offset ?

回答1:

>>> from dateutil.parser import parse
>>> dt = parse("2013-12-02 22:00:00" + "GMT+0800")
>>> dt.isoformat()
'2013-12-02T22:00:00-08:00'

Note: the sign is reversed.

You could also do it using only stdlib:

>>> from datetime import datetime
>>> dt = datetime.strptime("2013-12-02 22:00:00", "%Y-%m-%d %H:%M:%S")
>>> dt = dt.replace(tzinfo=FixedOffset(-8*60, "GMT+0800"))
>>> dt.isoformat()
'2013-12-02T22:00:00-08:00'

where FixedOffset is taken from datetime docs:

from datetime import tzinfo, timedelta

class FixedOffset(tzinfo):
    """Fixed offset in minutes east from UTC."""

    def __init__(self, offset, name):
        self.__offset = timedelta(minutes = offset)
        self.__name = name

    def utcoffset(self, dt):
        return self.__offset

    def tzname(self, dt):
        return self.__name

    def dst(self, dt):
        return timedelta(0)

Here's the same using pytz module:

>>> from datetime import datetime
>>> import pytz
>>> dt = datetime.strptime("2013-12-02 22:00:00", "%Y-%m-%d %H:%M:%S")
>>> dt = pytz.timezone('Etc/GMT+8').localize(dt)
>>> dt.isoformat()
'2013-12-02T22:00:00-08:00'

回答2:

Here are two approaches you could use:

>>> import datetime
>>> dtnow = datetime.datetime.now();dtutcnow = datetime.datetime.utcnow()
>>> dtnow
datetime.datetime(2013, 11, 12, 9, 10, 48, 404000)
>>> dtutcnow
datetime.datetime(2013, 11, 12, 15, 10, 48, 404000)
>>> delta = dtnow - dtutcnow
>>> delta
datetime.timedelta(-1, 64800)
>>> hh,mm = divmod((delta.days * 24*60*60 + delta.seconds + 30) // 60, 60)
>>> hh,mm
(-6, 0)
>>> "%s%+02d:%02d" % (dtnow.isoformat(), hh, mm)
'2013-11-12T09:10:48.404000-6:00'

Or this:

>>> import datetime, pytz # 3rd Party
>>> datetime.datetime.now(pytz.timezone('US/Central')).strftime('%Y-%m-%dT%H:%M:%S.%f%z')
'2013-11-12T09:15:20.688000-0600'
>>>

The main advantage of the second method is it makes your time string 'timezone aware'. From the docs:

There are two kinds of date and time objects: “naive” and “aware”. This distinction refers to whether the object has any notion of time zone, daylight saving time, or other kind of algorithmic or political time adjustment. Whether a naive datetime object represents Coordinated Universal Time (UTC), local time, or time in some other timezone is purely up to the program, just like it’s up to the program whether a particular number represents metres, miles, or mass. Naive datetime objects are easy to understand and to work with, at the cost of ignoring some aspects of reality.

Hope this helps!

来源：https://stackoverflow.com/questions/19932429/get-tz-offset-from-string

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python

datetime

python-dateutil

python-datetime