Question

If have the following Django (1.4) model:

from django.db import models

class SimpleModel(models.Model):
    name = models.CharField(max_length=100)

And this simple test:

from django.test import TestCase
from models import SimpleModel
from django.db import IntegrityError

class SimpleTest(TestCase):
    def test_integrity_error(self):
        with self.assertRaises(IntegrityError):
            m = SimpleModel()
            m.save()

As database a sqlite3 database is used. If I now run the tests with python manage.py test <appname> the test fails with AssertionError: IntegrityError not raised.

The question is: why?

As far as I understand (or thought to understand) Django the default values for Fields are blank=False and null=False so I would assume that saving an model instance with the default value (which I think for a CharField should be an empty string) should certainly fail! So, why doesn’t this happen?

Answer 1

Django never stores NULL for empty CharField or TextField types. It stores an empty string (''). So that’s why you don’t get an IntegrityError for null=False.

As for blank=False, that only affects forms. It just makes the form set the field as required=True so it won’t validate unless it has a value. It doesn’t affect the database or your ability to manually set a blank value outside of a form.