How can i compare two DateTimeFields with current time

Question

Event has two DateTimeField's and i need to compare them to the actual date time in a same method.

from django.utils import timezone

event_starts = models.DateTimeField(_("Event starts"))
registration_closes_at = models.DateTimeField(
        _("Registration ends:"), null=True, blank=True
    )

This is what i have tried, but it doesn't work. So what i need is: If event has been started or registration was closed user can not attend this event.

    def is_registration_open(self):
    now = timezone.now()
    passed_registration = now > self.registration_closes_at
    passed_start = now > self.event_starts

    if not passed_registration or not passed_start:
        return

And tried this:

def is_registration_open(self):

    if (
        not timezone.now() > self.registration_closes_at
        or not timezone.now() > self.event_starts
    ):
        return

Here is a fail:

'>' not supported between instances of 'datetime.datetime' and 'NoneType'

When i compare only event_starts everything is working fine.

Thanks for help!

Answer 1

Notice that registration_closes_at field is nullable, therefore you need to handle that case in the condition.

My guess is that you would like to ignore the registration_closes_at when it is null, so the condition would look like:

def is_registration_open(self):
    if self.registration_closes_at:
        # before registration closes
        return timezone.now() < self.registration_closes_at
    else:
        # before event starts
        return timezone.now() < self.event_starts

Even better option is to use annotation and check the condition on the database for better performance

from django.db.models import Count, Case, When, Value, BooleanField
from django.db.models.functions import Now

MyModel.objects.annotate(
    can_register=Case(
        When(registration_closes_at__gt=Now(), then=Value(True)),
        When(event_starts__gt=Now(), then=Value(True)),
        default=Value(False),
        output_field=BooleanField(),
    )
)