dateutil.parser.parse（）和丢失的时区信息 [英] dateutil.parser.parse() and lost timezone information

问题描述

我正在尝试 dateutil.parser.parse（）来解析默认的 str（datetime.datetime.now（））输出使用时区感知数据时间。但是， parse（）似乎丢失了时区信息，并将其替换为本地时区。以下是IPython输出：

I am trying to dateutil.parser.parse() to parse the default str(datetime.datetime.now()) output using timezone-aware datetimes. However, parse() seems to lose the timezone information and replace it with the local time timezone. Below is the IPython output:

In [1]: from django.utils.timezone import now
In [3]: import dateutil
In [4]: t = now()
In [6]: print t
2014-07-14 08:51:49.123342+00:00

In [7]: st = unicode(t)
In [8]: print dateutil.parser.parse(st)
2014-07-14 08:51:49.123342+02:00

到目前为止，我了解 dateutil 某些heurestics在猜测日期格式，可能会出现错误。

As far I understood dateutil does some heurestics when guessing the date format and it might go wrong here.

• 如何给出精确的datetime格式解析时区感知datetimes？

• How to give exact datetime format for parsing timezone-aware datetimes?

更好的 - 如果格式是已知的如何解析这个datetime只使用Python stdlib，没有dateutil依赖？

Even better - if the format is known how to parse this datetime using only Python stdlib, without dateutil dependency?

推荐答案

timezone.now 会给你一个感知的datetime对象，如果 USE_TZ 是true 。您不需要进一步解析。

timezone.now will give you an aware datetime object if USE_TZ is true. You don't need to parse it further.

在此示例中，USE_TZ为True，时区设置为UTC：

In this example, USE_TZ is True, and the timezone is set to UTC:

>>> from django.utils import timezone as djtz
>>> i = djtz.now()
>>> type(i)
<type 'datetime.datetime'>
>>> i.tzinfo
<UTC>

至于dateutil，它会正确解析你的字符串：

As far as dateutil goes, it will parse your string correctly:

>>> from dateutil.parser import parse
>>> s = '2014-07-14 08:51:49.123342+00:00'
>>> parse(s).tzinfo
tzutc()
>>> z = parse(s)
>>> z
datetime.datetime(2014, 7, 14, 8, 51, 49, 123342, tzinfo=tzutc())

您可以看到它拾起正确的时区（在这种情况下为UTC）。

You can see its picking up the correct timezone (UTC in this case).

默认格式说明符只接受+0000作为偏移格式，％ z ，或三字母的时区名称与％Z ;但是您不能使用这个来解析，只能使用格式：

The default format specifiers only accept +0000 as the offset format with %z, or the three letter timezone name with %Z; but you cannot use this to parse, only to format:

>>> datetime.datetime.strptime('2014-07-14 08:51:49.123342+0000', '%Y-%m-%d %H:%M:%S.%f%z')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.7/_strptime.py", line 317, in _strptime
    (bad_directive, format))
ValueError: 'z' is a bad directive in format '%Y-%m-%d %H:%M:%S.%f%z'
>>> datetime.datetime.strftime(z, '%Z')
'UTC'
>>> datetime.datetime.strftime(z, '%z')
'+0000'

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