如何在 Django 中舍入一个时区感知日期

Question

我正在尝试将默认时区 datetime 转换为 localtime 并将时间舍入到 Django 视图中的 15 分钟时隙。我有以下 roundTime 函数：

def roundTime(dt=None, dateDelta=timedelta(minutes=1)):
    """Round a datetime object to a multiple of a timedelta
    dt : datetime.datetime object, default now.
    dateDelta : timedelta object, we round to a multiple of this, default 1 minute.
    Author: Thierry Husson 2012 - Use it as you want but don't blame me.
            Stijn Nevens 2014 - Changed to use only datetime objects as variables
    """
    roundTo = dateDelta.total_seconds()

    if dt == None:
        dt = datetime.now()
    seconds = (dt - dt.min).seconds
    # // is a floor division, not a comment on following line:
    rounding = (seconds+roundTo/2) // roundTo * roundTo
    return dt + timedelta(0,rounding-seconds,-dt.microsecond)

这是我目前尝试过的方法：

mytime = roundTime(datetime.now(),timedelta(minutes=15)).strftime('%H:%M:%S') #works OK
mytime = datetime.strptime(str(mytime), '%H:%M:%S') #works OK
mytime = timezone.localtime(mytime)

但是最后一行给我这个错误：

error: astimezone() cannot be applied to a naive datetime

当我使用时：

local_time = timezone.localtime(timezone.now())

我确实得到了正确的当地时间，但由于某些原因我无法通过以下方式计算时间：

mytime = roundTime(local_time,timedelta(minutes=15)).strftime('%H:%M:%S')

与上面的 datetime.now() 一起使用。

我想出了这个不漂亮但可以工作的代码：

mytime = timezone.localtime(timezone.now())
mytime = datetime.strftime(mytime, '%Y-%m-%d %H:%M:%S')
mytime = datetime.strptime(str(mytime), '%Y-%m-%d %H:%M:%S')
mytime = roundTime(mytime,timedelta(minutes=15)).strftime('%H:%M:%S')
mytime = datetime.strptime(str(mytime), '%H:%M:%S')

有更好的解决方案吗？

Answer 1

您使用的 roundTime 函数不适用于时区感知日期。要支持它，您可以这样修改它：

def roundTime(dt=None, dateDelta=timedelta(minutes=1)):
    """Round a datetime object to a multiple of a timedelta
    dt : datetime.datetime object, default now.
    dateDelta : timedelta object, we round to a multiple of this, default 1 minute.
    Author: Thierry Husson 2012 - Use it as you want but don't blame me.
            Stijn Nevens 2014 - Changed to use only datetime objects as variables
    """
    roundTo = dateDelta.total_seconds()

    if dt == None : 
        dt = datetime.now()
    #Make sure dt and datetime.min have the same timezone
    tzmin = dt.min.replace(tzinfo=dt.tzinfo)

    seconds = (dt - tzmin).seconds
    # // is a floor division, not a comment on following line:
    rounding = (seconds+roundTo/2) // roundTo * roundTo
    return dt + timedelta(0,rounding-seconds,-dt.microsecond)

通过这种方式，该函数既适用于原始日期，也适用于 TZ 感知日期。然后您可以像第二次尝试一样继续：

local_time = timezone.localtime(timezone.now()) 
mytime = roundTime(local_time, timedelta(minutes=15))

Answer 2

要舍入可识别时区的日期时间对象，make it a naive datetime object, round it, and attach the correct time zone info for the rounded time:

from datetime import timedelta
from django.utils import timezone

def round_time(dt=None, delta=timedelta(minutes=1)):
    if dt is None:
        dt = timezone.localtime(timezone.now()) # assume USE_TZ=True
    tzinfo, is_dst = dt.tzinfo, bool(dt.dst())
    dt = dt.replace(tzinfo=None)
    f = delta.total_seconds()
    rounded_ordinal_seconds = f * round((dt - dt.min).total_seconds() / f)
    rounded_dt = dt.min + timedelta(seconds=rounded_ordinal_seconds)
    localize = getattr(tzinfo, 'localize', None)
    if localize:
        rounded_dt = localize(rounded_dt, is_dst=is_dst)
    else:
        rounded_dt = rounded_dt.replace(tzinfo=tzinfo)
    return rounded_dt

为避免浮点问题，所有计算都可以使用整数微秒 (dt.resolution) 重写。

示例：

>>> round_time(delta=timedelta(minutes=15))

如何在 Django 中舍入一个时区感知日期

How to round a timezone-aware date in Django

python

django

timezone

datetime