Getting TypeError: __init__() missing 1 required p

Question

I have two classes in my sqlite database, a parent table named Categorie and the child table called Article. I created first the child table class and addes entries. So first I had this:

class Article(models.Model):
    titre=models.CharField(max_length=100)
    auteur=models.CharField(max_length=42)
    contenu=models.TextField(null=True)
    date=models.DateTimeField(
        auto_now_add=True,
        auto_now=False,
        verbose_name="Date de parution"
    )

    def __str__(self):
        return self.titre

And after I have added parent table, and now my models.py looks like this:

from django.db import models

# Create your models here.
class Categorie(models.Model):
    nom = models.CharField(max_length=30)

    def __str__(self):
        return self.nom


class Article(models.Model):
    titre=models.CharField(max_length=100)
    auteur=models.CharField(max_length=42)
    contenu=models.TextField(null=True)
    date=models.DateTimeField(
        auto_now_add=True,
        auto_now=False,
        verbose_name="Date de parution"
    )
    categorie = models.ForeignKey('Categorie')

    def __str__(self):
        return self.titre

So when I run python manage.py makemigrations <my_app_name>, I get this error:

Traceback (most recent call last):
  File "manage.py", line 15, in <module>
    execute_from_command_line(sys.argv)
  File "C:\Users\lislis\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django-2.0-py3.5.egg\django\core\management\__init__.py", line 354, in execute_from_command_line
    utility.execute()
  File "C:\Users\lislis\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django-2.0-py3.5.egg\django\core\management\__init__.py", line 330, in execute
    django.setup()
  File "C:\Users\lislis\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django-2.0-py3.5.egg\django\__init__.py", line 24, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "C:\Users\lislis\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django-2.0-py3.5.egg\django\apps\registry.py", line 112, in populate
    app_config.import_models()
  File "C:\Users\lislis\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django-2.0-py3.5.egg\django\apps\config.py", line 198, in import_models
    self.models_module = import_module(models_module_name)
  File "C:\Users\lislis\AppData\Local\Programs\Python\Python35-32\lib\importlib\__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 986, in _gcd_import
  File "<frozen importlib._bootstrap>", line 969, in _find_and_load
  File "<frozen importlib._bootstrap>", line 958, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 673, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 665, in exec_module
  File "<frozen importlib._bootstrap>", line 222, in _call_with_frames_removed
  File "C:\Users\lislis\Django\mon_site\blog\models.py", line 6, in <module>
    class Article(models.Model):
  File "C:\Users\lislis\Django\mon_site\blog\models.py", line 16, in Article
    categorie = models.ForeignKey('Categorie')
TypeError: __init__() missing 1 required positional argument: 'on_delete'

I've seen some similar issues in stackoverflow, but it seems to not be the same problem: __init__() missing 1 required positional argument: 'quantity'

Answer 1

Since Django 2.x, on_delete is required.

Django Documentation

Deprecated since version 1.9: on_delete will become a required argument in Django 2.0. In older versions it defaults to CASCADE.

Answer 2

Up until Django 1.9 a model would look like the following:

from django.db import models
class Article(models.Model):
    category = models.ForeignKey(Category)
    title =  models.CharField(max_length=55)
    # ...

    def __str__(self):
        return self.title

ForeignKey is a Django field for defining a many-to-one relationship.

Up until Django 1.9 the ForeignKey field required a single argument: the model to map to.

Since Django 2.0 the ForeignKey field requires two positional arguments:

1- the model to map to

2-the on_delete argument

For a quick fix of “missing 1 required positional argument: on_delete” update the model:

from django.db import models
class Article(models.Model):
    category = models.ForeignKey('Category', on_delete=models.PROTECT)
    title =  models.CharField(max_length=55)
    # ...

    def __str__(self):
        return self.title

After fixing ForeignKey you’ll be able to run migrations without any trouble:

python manage.py migrate

Thanks to Valentino

Answer 3

If you are using foreignkey then you have to use "on_delete=models.CASCADE" as it will eliminate the complexity developed after deleting the original element from the parent table. As simple as that.

categorie = models.ForeignKey('Categorie', on_delete=models.CASCADE)

Answer 4

You can change the property categorie of the class Article like this:

categorie = models.ForeignKey(
    'Categorie',
    on_delete=models.CASCADE,
)

and the error should disappear.

Eventually you might need another option for on_delete, check the documentation for more details:

https://docs.djangoproject.com/en/1.11/ref/models/fields/#django.db.models.ForeignKey

EDIT:

As you stated in your comment, that you don't have any special requirements for on_delete, you could use the option DO_NOTHING:

# ...
on_delete=models.DO_NOTHING,
# ...

Answer 5

Here are available options if it helps anyone for on_delete

CASCADE, DO_NOTHING, PROTECT, SET, SET_DEFAULT, SET_NULL

Answer 6

From Django 2.0 on_delete is required:

user = models.OneToOneField(User, on_delete=models.CASCADE)

It will delete the child table data if the User is deleted. For more details check the Django documentation.