Uploaded and Deadline fields in Django models - django

Question

I am making a to do app and in models I have a Task model and dateTimeFields "uploaded", which has auto_now_add=True. Now I want to add deadline field, where users can add the task deadlines. I tried adding second DateTimeField but there's a problem when I make migrations. here's the code and the powershell warning:
models:
class Task(models.Model):
title = models.CharField(max_length=50)
completed = models.BooleanField(default=False)
uploaded = models.DateTimeField(auto_now_add=True)
deadline = models.DateTimeField()
def __str__(self):
return self.title
powershell:
*You are trying to add a non-nullable field 'deadline' to task without a default; we can't do that (the database needs something to populate existing rows).
Please select a fix:
Provide a one-off default now (will be set on all existing rows with a null value for this column)
Quit, and let me add a default in models.py
Select an option:*

Answer 1

But there's a problem when I make migrations.
The problem is that the database might already have records, so what will you do to the Tasks in the database that now need a value for the existing records.
You can for example decide to work with the current timestamp. You can do this by selecting 1, and then work with timezone.now:
You are trying to add a non-nullable field 'deadline' to task without a default; we can't do that (the database needs something to populate existing rows).
Please select a fix:
1) Provide a one-off default now (will be set on all existing rows with a null value for this column)
2) Quit, and let me add a default in models.py
Select an option: 1
Please enter the default value now, as valid Python
The datetime and django.utils.timezone modules are available, so you can do e.g. timezone.now
Type 'exit' to exit this prompt
>>> timezone.now
This will thus set the current timestamp to all the Tasks already in the database.
You can also decide to set it to a datetime in the future, for example 1-1-2100:
You are trying to add a non-nullable field 'deadline' to task without a default; we can't do that (the database needs something to populate existing rows).
Please select a fix:
1) Provide a one-off default now (will be set on all existing rows with a null value for this column)
2) Quit, and let me add a default in models.py
Select an option: 1
Please enter the default value now, as valid Python
The datetime and django.utils.timezone modules are available, so you can do e.g. timezone.now
Type 'exit' to exit this prompt
>>> datetime.datetime(2100, 1, 1)
Another alternative is to provide the default in the model itself, but then it also will take that default for new tasks and thus not only the tasks already recorded.
Often a field is made nullable in case one does not have to specify the current timestamp. In that case you thus specify null=True, and by default it will use NULL/None as default for the exiting records:
class Task(models.Model):
# …
deadline = models.DateTimeField(null=True)
# …

Answer 2

If deadline is added afterwards you create the model, you need to tell django that its a null able field, such that deadline can have no value. just add null=True in deadline field
class Task(models.Model):
title = models.CharField(max_length=50)
completed = models.BooleanField(default=False)
uploaded = models.DateTimeField(auto_now_add=True)
deadline = modles.DateTimeField(null=True)
def __str__(self):
return self.title