Django create object - use default value for None

Question

So I have a Django model which has few non nullable field with default values.

class Article(models.Model):
    id = models.UUIDField(default=uuid4, primary_key=True, editable=False)
    code = models.CharField(max_length=200, default=uuid4, unique=True, null=False)
    company = models.CharField(max_length=200, default=uuid4, unique=True, null=False)

Now i want to do a

Article.objects.get_or_create(company=company, code=am_row['Article code'])

But here the issue is am_row['Article code'] or company can be a None, and in that case i just want a new model to be created using that fields default values.

Currently passing None throws a NOT NULL constraint failed error. How can i achieve this?

So i think this boils down to achieving

Article.objects.create(company=company, code=am_row['Article code'])

have tried checking if either is none and if it is just creating a new object and saving it like obj = Foo.objects.create() obj.save() ? That should use the default values. You could also check if they are none and just pass in the default values — Taylor
– Taylor, Commented Feb 7, 2019 at 16:56
the am_row['Article code'] was None. So it was throwing this error. — Nithin
– Nithin, Commented Feb 7, 2019 at 16:57
@Taylor in this case i have only two variables, but what if i have more variables, checking if they are None and passing is not good option . — Nithin
– Nithin, Commented Feb 7, 2019 at 16:58

ruddra · Accepted Answer · 2019-02-07 17:56:32Z

2

You can override the get_or_create method in your model manager, like this:

class CustomManager(models.Manager):
    def get_or_create(self, **kwargs):
        defaults = kwargs.pop('defaults', {})  # popping defaults from values
        for key, value in kwargs.items():
            if value == None:
                kwargs[key] = defaults.get(key)
        return super(CustomManager, self).get_or_create(**kwargs)


class Article(models.Model):
    # ...
    objects = CustomManager()

Then use it in your view like this:

Article.objects.get_or_create(
     company=company,
     code=am_row.get('Article code'),
     defaults={
        'company': uuid.uuid4(),
        'code': uuid.uuid4()
     }
)

If you want the default functionality of get_or_create, then use:

objects = Article._base_manager
objects.get_or_create(...)

edited Feb 7, 2019 at 17:56

answered Feb 7, 2019 at 17:08

ruddra

52.1k7 gold badges82 silver badges105 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Nithin Over a year ago

but here what if am_row['Article code'] is not None. In that case i want to create the object with that value only not the default value.

ruddra Over a year ago

Yep, my mistake. I missed that part of documentation. Updating my answer shortly

Nithin Over a year ago

awesome , Thanks

gonczor · Accepted Answer · 2019-02-07 17:18:20Z

1

I'd use or operator in this case. Look at the example. If x is None some default value will be passed:

In [1]: import uuid

In [2]: def some_function(something):
   ...:     print(f'Something is {something}')
   ...:

In [3]: x = None

In [4]: some_function(x or uuid.uuid4())
Something is 518d7187-f74d-4620-90de-6104698a7d07

In [5]: x = 'Hello, world!'

In [6]: some_function(x or uuid.uuid4())
Something is Hello, world!

edited Feb 7, 2019 at 17:18

answered Feb 7, 2019 at 16:55

gonczor

4,1841 gold badge25 silver badges53 bronze badges

1 Comment

Nithin Over a year ago

cool, i didn't knew we could use or directly while passing arguments

Collectives™ on Stack Overflow

Django create object - use default value for None

2 Answers 2

3 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related