How to get all objects referenced as ForeignKey from given field in a module in django

Question

I have two classes: Author and Book. I want class Authors to have an attribute that contains all books written by the said author, as referenced to as foreign key in the class Books. The method I did does not appear to be working, which I assume is because when the database is being created in migrations, no Books objects exist yet. Or so I believe, I'm pretty new at django.

class Author(models.Model):
    AuthorName = models.CharField(max_length=255, unique=True)
    books = Book.objects.get(pk=object_instance.pk)

class Book(models.Model):
    BookName = models.CharField(max_length=255)
    Author = models.ForeignKey('Author')

The error message I get is:

NameError: name 'Book' is not defined

Which I get, is because I'm referencing to another class without actually having and instance of that class. I just can't figure out a proper way to do this.

EDIT: I reformatted it to be like this:

class Author(models.Model):
    AuthorName = models.CharField(max_length=255, unique=True)
    books = author.book_set.all()

class Book(models.Model):
    BookName = models.CharField(max_length=255)
    Author = models.ForeignKey('Author')

which yields error:

NameError: name 'author' is not defined

Maybe I should just query for the datapoints I need later on in views as opposed to creating own field for them in models though..

EDIT 2: solution from answers:

So my mistake all along was to try to add the "books" field in the author table. I guess there's no way to do this then. I can get that method to work in views so I guess this is sort of solved, although not in the way I was originally planning to do it.

doing

class Author(models.Model):
    AuthorName = models.CharField(max_length=255, unique=True)

class Book(models.Model):
    BookName = models.CharField(max_length=255)
    Author = models.ForeignKey('Author')

and then later doing this in views:

author = Author.objects.get(pk=1)
books = author.book_get.all()

yields the wanted result (which I sort of knew beforehand, but I was trying to implement a books field in the models, which, if i correctly understood, is not possible at least not with this method).

another solution:

class Author(models.Model):
    AuthorName = models.CharField(max_length=255, unique=True)

class Book(models.Model):
    BookName = models.CharField(max_length=255)
    Author = models.ForeignKey(Author, related_name = "books")

Answer 1

You don't need to create a separate field in Authors model

class Author(models.Model):
    AuthorName = models.CharField(max_length=255, unique=True)

class Book(models.Model):
    BookName = models.CharField(max_length=255)
    Author = models.ForeignKey('Author')

You can get all books of a particular author like:

author = Author.objects.get(id=1)
books = author.book_set.all()

Learn more about backward relationships here

Answer 2

Just add related_name to ForeignKey and you will be able to get all books made by an author.

For example:

class Book(models.Model):
    ...
    author = models.ForeignKey('Author', related_name='books')
    ...

and later...

author = Author.objects.get(pk=1)
books = author.books.all()

Answer 3

You did something weird in line:

books = Book.objects.get(pk=object_instance.pk)

Just delete it. You will be able to use author.book_set. You can also use related_name parameter of ForeignKey.

See the Django docs: https://docs.djangoproject.com/en/4.0/ref/models/fields/#foreignkey