Question

I try to save user’s birth date, but get “null value in column “dob” violates not-null constraint” error.

models.py:

class Profile(models.Model):
  user = models.OneToOneField(User, unique=True)

  nickname = models.CharField(max_length=32)
  dob = models.DateField(null=False)
  sex = models.BooleanField(null=False)

Here i try to generate random users:

def create_random_users(userCount=1000):
  random.seed()

  for i in range(0, userCount):
    sex = random.randint(0, 1)
    name = random.choice(names[sex])

    email = "{0}{1}@mail.com".format(name, i)
    user = soc_models.User.objects.create_user(email, email, password='password')
    user.save()

    userProfile = soc_models.Profile.objects.create()
    userProfile.user = user
    _year = random.randrange(1962, 1995)
    _month = random.randrange(1, 12)
    _day = random.randrange(1, calendar.monthrange(_year, _month)[1])
    userProfile.dob = datetime.datetime(_year, _month, _day)

    userProfile.sex = random.randrange(0, 1)
    userProfile.city = random.randrange(4000000)
    userProfile.country = random.randrange(230)
    userProfile.save()

Thank you.

Answer 1

The create method is documented as “a convenience method for creating an object and saving it all in one step”. So when the following statement in your sample data creation script runs:

userProfile = soc_models.Profile.objects.create()

It attempts to save an empty Profile object to the database. Since you haven’t set the dob attribute at this point, you trigger the NOT NULL constraint.

Two ways to avoid this are:

1. create the object via the constructor so that it isn’t immediately saved to the database.
2. provide values for all the fields via keyword arguments to create.