Can't compare naive and aware datetime.now() <= challenge.datetime_end
Question:
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?
Answers:
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)
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
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.
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.
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):
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.
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
You are trying to set the timezone for date_time which already has a timezone.
Use replace and astimezone functions.
local_tz = pytz.timezone('Asia/Kolkata')
current_time = datetime.now().replace(tzinfo=pytz.utc).astimezone(local_tz)
no third-party, only the native datetime module.
from datetime import datetime, timedelta, timezone
time1 = datetime.strptime('2021-07-15T00:22:02+0000', '%Y-%m-%dT%H:%M:%S%z')
time2 = datetime(2021, 7, 15, tzinfo=timezone(offset=timedelta()))
if time1 < time2:
print(True)
If you are using SQLAlchemy and storing the DateTime then you can store it with timezone info. This will allow you to compare that DateTime with timezone-aware DateTimes. Example Column definition in SQLAlchemy core:
Column("created_at", DateTime(timezone=True), nullable=False)
If you’re using Python 3.6 and newer, you can leverage the native datetime capability.
utc_date = datetime.datetime.fromtimestamp(0, datetime.timezone.utc)
In my case I have controlled the time zone with pytz and I have converted the date to native with timezone from django.utils:
import pytz
from django.utils import timezone
def _my_method(native_date, timezone):
aware_date = datetime.now(pytz.timezone(timezone))
return timezone.make_naive(aware_date) > native_date
Also you can make aware the native date with timezone.make_aware
To make your datetime object timezone aware from naive, simply add the function:
datetimeObject.astimezone()
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?
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)
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
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.
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.
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):
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.
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
You are trying to set the timezone for date_time which already has a timezone.
Use replace and astimezone functions.
local_tz = pytz.timezone('Asia/Kolkata')
current_time = datetime.now().replace(tzinfo=pytz.utc).astimezone(local_tz)
no third-party, only the native datetime module.
from datetime import datetime, timedelta, timezone
time1 = datetime.strptime('2021-07-15T00:22:02+0000', '%Y-%m-%dT%H:%M:%S%z')
time2 = datetime(2021, 7, 15, tzinfo=timezone(offset=timedelta()))
if time1 < time2:
print(True)
If you are using SQLAlchemy and storing the DateTime then you can store it with timezone info. This will allow you to compare that DateTime with timezone-aware DateTimes. Example Column definition in SQLAlchemy core:
Column("created_at", DateTime(timezone=True), nullable=False)
If you’re using Python 3.6 and newer, you can leverage the native datetime capability.
utc_date = datetime.datetime.fromtimestamp(0, datetime.timezone.utc)
In my case I have controlled the time zone with pytz and I have converted the date to native with timezone from django.utils:
import pytz
from django.utils import timezone
def _my_method(native_date, timezone):
aware_date = datetime.now(pytz.timezone(timezone))
return timezone.make_naive(aware_date) > native_date
Also you can make aware the native date with timezone.make_aware
To make your datetime object timezone aware from naive, simply add the function:
datetimeObject.astimezone()