Question

I have a question. Will these two properties work different and how, I mean db hits.
for example, we have the model Article, that has a ForeignKey field book

from django.db import models

class Article(models.Model):
    book = models.ForeignKey("books.Book")

what is the best way to get an author by one of the prorerties:

@property
def author(self):
    if self.book:
        return self.book.author
    return None

or

@property
def author(self):
    book = self.book
    if book:
        return book.author
    return None

Answer 1

Since you are defining a property on Article, the actual database hit depends on how Article querysets are retrieved. If you use select_related([depth=2]) on your queryset while retrieving the Article objects, that would be the most optimal in terms of database hits irrespective of how you write the property. Both the ways you have listed have similar performance.