[1.4.X] Fixed #17436 - Added warning about overriding Model.__init__()

model. Note that instantiating a model in no way touches your database; for

that, you need to :meth:`~Model.save()`.

.. note::

    You may be tempted to customize the model by overriding the ``__init__``

    method. If you do so, however, take care not to change the calling

    signature as any change may prevent the model instance from being saved.

    Rather than overriding ``__init__``, try using one of these approaches:

    1. Add a classmethod on the model class::

        class Book(models.Model):

            title = models.CharField(max_length=100)

            @classmethod

            def create(cls, title):

                book = cls(title=title)

                # do something with the book

                return book

        book = Book.create("Pride and Prejudice")

    2. Add a method on a custom manager (usually preferred)::

        class BookManager(models.Manager):

            def create_book(title):

                book = self.create(title=title)

                # do something with the book

                return book

        class Book(models.Model):

            title = models.CharField(max_length=100)

            objects = BookManager()

        book = Book.objects.create_book("Pride and Prejudice")

.. _validating-objects:

Validating objects

Note that in the case of identical date values, these methods will use the

primary key as a tie-breaker. This guarantees that no records are skipped or

duplicated. That also means you cannot use those methods on unsaved objects.