无法比较幼稚和知道的datetime.now（）

2021-08-04 知识问答 0 0 1.3K

问题：无法比较幼稚和知道的datetime.now（）

我正在尝试使用比较运算符将当前日期和时间与模型中指定的日期和时间进行比较：

if challenge.datetime_start <= datetime.now() <= challenge.datetime_end:

脚本错误如下：

TypeError: can't compare offset-naive and offset-aware datetimes

这些模型如下所示：

class Fundraising_Challenge(models.Model):
    name = models.CharField(max_length=100)
    datetime_start = models.DateTimeField()
    datetime_end = models.DateTimeField()

我也有使用区域设置日期和时间的django。

我找不到的是django用于DateTimeField（）的格式。天真还是知道？以及如何获取datetime.now（）来识别语言环境datetime？

点击查看英文原文

I am trying to compare the current date and time with dates and times specified in models using comparison operators:

if challenge.datetime_start <= datetime.now() <= challenge.datetime_end:

The script errors out with:

TypeError: can't compare offset-naive and offset-aware datetimes

The models look like this:

class Fundraising_Challenge(models.Model):
    name = models.CharField(max_length=100)
    datetime_start = models.DateTimeField()
    datetime_end = models.DateTimeField()

I also have django using locale date and times.

What I haven’t been able to find is the format django uses for DateTimeField(). Is it naive or aware? And how do I get datetime.now() to recognize locale datetime?

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回答 0

默认情况下，该datetime对象naive位于Python中，因此您需要将它们都设为天真或感知datetime对象。可以使用以下方法完成：

import datetime
import pytz

utc=pytz.UTC

challenge.datetime_start = utc.localize(challenge.datetime_start) 
challenge.datetime_end = utc.localize(challenge.datetime_end) 
# now both the datetime objects are aware, and you can compare them

注意：这将引发一个ValueErrorif tzinfo值。如果您不确定，请使用

start_time = challenge.datetime_start.replace(tzinfo=utc)
end_time = challenge.datetime_end.replace(tzinfo=utc)

顺便说一句，您可以在带有时区信息的datetime.datetime对象中格式化UNIX时间戳，如下所示

d = datetime.datetime.utcfromtimestamp(int(unix_timestamp))
d_with_tz = datetime.datetime(
    year=d.year,
    month=d.month,
    day=d.day,
    hour=d.hour,
    minute=d.minute,
    second=d.second,
    tzinfo=pytz.UTC)

点击查看英文原文

By default, the datetime object is naive in Python, so you need to make both of them either naive or aware datetime objects. This can be done using:

import datetime
import pytz

utc=pytz.UTC

challenge.datetime_start = utc.localize(challenge.datetime_start) 
challenge.datetime_end = utc.localize(challenge.datetime_end) 
# now both the datetime objects are aware, and you can compare them

Note: This would raise a ValueError if tzinfo is already set. If you are not sure about that, just use

start_time = challenge.datetime_start.replace(tzinfo=utc)
end_time = challenge.datetime_end.replace(tzinfo=utc)

BTW, you could format a UNIX timestamp in datetime.datetime object with timezone info as following

d = datetime.datetime.utcfromtimestamp(int(unix_timestamp))
d_with_tz = datetime.datetime(
    year=d.year,
    month=d.month,
    day=d.day,
    hour=d.hour,
    minute=d.minute,
    second=d.second,
    tzinfo=pytz.UTC)

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回答 1

datetime.datetime.now 不了解时区。

Django为此提供了一个帮助程序，它需要 pytz

from django.utils import timezone
now = timezone.now()

你应该能够比较now来challenge.datetime_start

点击查看英文原文

datetime.datetime.now is not timezone aware.

Django comes with a helper for this, which requires pytz

from django.utils import timezone
now = timezone.now()

You should be able to compare now to challenge.datetime_start

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回答 2

一行代码解决方案

if timezone_aware_var <= datetime.datetime.now(timezone_aware_var.tzinfo):
    pass #some code

解释版

# Timezone info of your timezone aware variable
timezone = your_timezone_aware_variable.tzinfo

# Current datetime for the timezone of your variable
now_in_timezone = datetime.datetime.now(timezone)

# Now you can do a fair comparison, both datetime variables have the same time zone
if your_timezone_aware_variable <= now_in_timezone:
    pass #some code

摘要

您必须将时区信息添加到now()日期时间。
但是，您必须添加参考变量的相同时区。这就是为什么我首先阅读该tzinfo属性的原因。

点击查看英文原文

One line of code solution

if timezone_aware_var <= datetime.datetime.now(timezone_aware_var.tzinfo):
    pass #some code

Explained version

# Timezone info of your timezone aware variable
timezone = your_timezone_aware_variable.tzinfo

# Current datetime for the timezone of your variable
now_in_timezone = datetime.datetime.now(timezone)

# Now you can do a fair comparison, both datetime variables have the same time zone
if your_timezone_aware_variable <= now_in_timezone:
    pass #some code

Summary

You must add the timezone info to your now() datetime.
However, you must add the same timezone of the reference variable; that is why I first read the tzinfo attribute.

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回答 3

禁用时区。用challenge.datetime_start.replace(tzinfo=None);

您还可以将其replace(tzinfo=None)用于其他datetime。

if challenge.datetime_start.replace(tzinfo=None) <= datetime.now().replace(tzinfo=None) <= challenge.datetime_end.replace(tzinfo=None):

点击查看英文原文

Disable time zone. Use challenge.datetime_start.replace(tzinfo=None);

You can also use replace(tzinfo=None) for other datetime.

if challenge.datetime_start.replace(tzinfo=None) <= datetime.now().replace(tzinfo=None) <= challenge.datetime_end.replace(tzinfo=None):

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回答 4

因此，我要解决此问题的方法是确保两个日期时间在正确的时区中。

我可以看到您正在使用datetime.now()它将返回系统的当前时间，而未设置tzinfo。

tzinfo是附加在日期时间上的信息，以使其知道它所在的时区。如果使用的是朴素的日期时间，则需要在整个系统中保持一致。我强烈建议只使用datetime.utcnow()

看到您正在创建与tzinfo相关联的日期时间，您需要做的是确保将它们本地化（与tzinfo相关联）到正确的时区。

看一下Delorean，它使处理这种事情变得更加容易。

点击查看英文原文

So the way I would solve this problem is to make sure the two datetimes are in the right timezone.

I can see that you are using datetime.now() which will return the systems current time, with no tzinfo set.

tzinfo is the information attached to a datetime to let it know what timezone it is in. If you are using naive datetime you need to be consistent through out your system. I would highly recommend only using datetime.utcnow()

seeing as somewhere your are creating datetime that have tzinfo associated with them, what you need to do is make sure those are localized (has tzinfo associated) to the correct timezone.

Take a look at Delorean, it makes dealing with this sort of thing much easier.

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回答 5

这是我的工作。在这里，我对创建的日期时间的表进行geet，并在日期时间上添加10分钟。稍后根据当前时间，完成到期操作。

from datetime import datetime, time, timedelta
import pytz

在数据库日期时间增加了10分钟

table_datetime =’2019-06-13 07：49：02.832969’（示例）

# Added 10 minutes on database datetime
# table_datetime = '2019-06-13 07:49:02.832969' (example)

table_expire_datetime = table_datetime + timedelta(minutes=10 )

# Current datetime
current_datetime = datetime.now()


# replace the timezone in both time
expired_on = table_expire_datetime.replace(tzinfo=utc)
checked_on = current_datetime.replace(tzinfo=utc)


if expired_on < checked_on:
    print("Time Crossed)
else:
    print("Time not crossed ")

它为我工作。

点击查看英文原文

It is working form me. Here I am geeting the table created datetime and adding 10 minutes on the datetime. later depending on the current time, Expiry Operations are done.

from datetime import datetime, time, timedelta
import pytz

Added 10 minutes on database datetime

table_datetime = ‘2019-06-13 07:49:02.832969’ (example)

# Added 10 minutes on database datetime
# table_datetime = '2019-06-13 07:49:02.832969' (example)

table_expire_datetime = table_datetime + timedelta(minutes=10 )

# Current datetime
current_datetime = datetime.now()


# replace the timezone in both time
expired_on = table_expire_datetime.replace(tzinfo=utc)
checked_on = current_datetime.replace(tzinfo=utc)


if expired_on < checked_on:
    print("Time Crossed)
else:
    print("Time not crossed ")

It worked for me.

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回答 6

只是：

dt = datetimeObject.strftime(format) # format = your datetime format ex) '%Y %d %m'
dt = datetime.datetime.strptime(dt,format)

这样做：

start_time = challenge.datetime_start.strftime('%Y %d %m %H %M %S')
start_time = datetime.datetime.strptime(start_time,'%Y %d %m %H %M %S')

end_time = challenge.datetime_end.strftime('%Y %d %m %H %M %S')
end_time = datetime.datetime.strptime(end_time,'%Y %d %m %H %M %S')

然后使用start_time和end_time

点击查看英文原文

Just:

dt = datetimeObject.strftime(format) # format = your datetime format ex) '%Y %d %m'
dt = datetime.datetime.strptime(dt,format)

So do this:

start_time = challenge.datetime_start.strftime('%Y %d %m %H %M %S')
start_time = datetime.datetime.strptime(start_time,'%Y %d %m %H %M %S')

end_time = challenge.datetime_end.strftime('%Y %d %m %H %M %S')
end_time = datetime.datetime.strptime(end_time,'%Y %d %m %H %M %S')

and then use start_time and end_time

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