如何使一个时区感知datetime对象

我需要做什么

我有一个不了解时区的datetime对象，我需要向它添加一个时区，以便能够将它与其他了解时区的datetime对象进行比较。我不想将我的整个应用程序转换为不知道这个遗留情况的时区。

我的努力

首先，演示问题:

Python 2.6.1 (r261:67515, Jun 24 2010, 21:47:49) 
[GCC 4.2.1 (Apple Inc. build 5646)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import datetime
>>> import pytz
>>> unaware = datetime.datetime(2011,8,15,8,15,12,0)
>>> unaware
datetime.datetime(2011, 8, 15, 8, 15, 12)
>>> aware = datetime.datetime(2011,8,15,8,15,12,0,pytz.UTC)
>>> aware
datetime.datetime(2011, 8, 15, 8, 15, 12, tzinfo=<UTC>)
>>> aware == unaware
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: can't compare offset-naive and offset-aware datetimes

首先，我尝试了astimezone:

>>> unaware.astimezone(pytz.UTC)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: astimezone() cannot be applied to a naive datetime
>>>

这个失败并不奇怪，因为它实际上是在尝试进行转换。Replace似乎是一个更好的选择(如如何在Python中获得“时区感知”的datetime.today()值?):

>>> unaware.replace(tzinfo=pytz.UTC)
datetime.datetime(2011, 8, 15, 8, 15, 12, tzinfo=<UTC>)
>>> unaware == aware
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: can't compare offset-naive and offset-aware datetimes
>>>

但正如您所看到的，replace似乎设置了tzinfo，但并没有使对象感知。我准备在解析输入字符串之前修改输入字符串以获得时区(如果有问题的话，我将使用dateutil进行解析)，但这似乎非常笨拙。

此外，我在Python 2.6和Python 2.7中都尝试了这一点，得到了相同的结果。

上下文

I am writing a parser for some data files. There is an old format I need to support where the date string does not have a timezone indicator. I've already fixed the data source, but I still need to support the legacy data format. A one time conversion of the legacy data is not an option for various business BS reasons. While in general, I do not like the idea of hard-coding a default timezone, in this case it seems like the best option. I know with reasonable confidence that all the legacy data in question is in UTC, so I'm prepared to accept the risk of defaulting to that in this case.

当前回答

这里有一个简单的解决方案，以尽量减少对代码的更改:

from datetime import datetime
import pytz

start_utc = datetime.utcnow()
print ("Time (UTC): %s" % start_utc.strftime("%d-%m-%Y %H:%M:%S"))

时间(UTC): 09-01-2021 03:49:03

tz = pytz.timezone('Africa/Cairo')
start_tz = datetime.now().astimezone(tz)
print ("Time (RSA): %s" % start_tz.strftime("%d-%m-%Y %H:%M:%S"))

时间(RSA): 09-01-2021 05:49:03

2021-01-09 03:45:12

其他回答

在时区之间更改

import pytz
from datetime import datetime

other_tz = pytz.timezone('Europe/Madrid')

# From random aware datetime...
aware_datetime = datetime.utcnow().astimezone(other_tz)
>> 2020-05-21 08:28:26.984948+02:00

# 1. Change aware datetime to UTC and remove tzinfo to obtain an unaware datetime
unaware_datetime = aware_datetime.astimezone(pytz.UTC).replace(tzinfo=None)
>> 2020-05-21 06:28:26.984948

# 2. Set tzinfo to UTC directly on an unaware datetime to obtain an utc aware datetime
aware_datetime_utc = unaware_datetime.replace(tzinfo=pytz.UTC)
>> 2020-05-21 06:28:26.984948+00:00

# 3. Convert the aware utc datetime into another timezone
reconverted_aware_datetime = aware_datetime_utc.astimezone(other_tz)
>> 2020-05-21 08:28:26.984948+02:00

# Initial Aware Datetime and Reconverted Aware Datetime are equal
print(aware_datetime1 == aware_datetime2)
>> True

2020-05-21 08:32:46

这是@Sérgio和@unutbu的答案。它将“只是工作”与任何一个pytz。对象或IANA时区字符串。

def make_tz_aware(dt, tz='UTC', is_dst=None):
    """Add timezone information to a datetime object, only if it is naive."""
    tz = dt.tzinfo or tz
    try:
        tz = pytz.timezone(tz)
    except AttributeError:
        pass
    return tz.localize(dt, is_dst=is_dst)

这似乎是datetime. localalize()(或.inform()或. aware())应该做的事情，为tz参数接受字符串和时区对象，如果没有指定时区，则默认为UTC。

2014-01-15 18:55:37

unutbu回答的格式;我做了一个实用模块，用更直观的语法来处理这样的事情。可以用pip安装。

import datetime
import saturn

unaware = datetime.datetime(2011, 8, 15, 8, 15, 12, 0)
now_aware = saturn.fix_naive(unaware)

now_aware_madrid = saturn.fix_naive(unaware, 'Europe/Madrid')

2016-09-25 23:31:51

我刚接触Python，遇到了同样的问题。我发现这个解决方案非常简单，对我来说它工作得很好(Python 3.6):

unaware=parser.parse("2020-05-01 0:00:00")
aware=unaware.replace(tzinfo=tz.tzlocal()).astimezone(tz.tzlocal())

2020-05-06 11:06:19

我在Django中使用这个语句将一个无意识的时间转换为一个有意识的时间:

from django.utils import timezone

dt_aware = timezone.make_aware(dt_unaware, timezone.get_current_timezone())

2015-01-27 15:21:38

如何使一个时区感知datetime对象

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