pythondjangodatetimecomparison

Can't compare naive and aware datetime.now() <= challenge.datetime_end


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?


Solution

  • 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)