👀 Views: 50 💬 Answers: 1 📅 Created: 2025-06-11

django signals models Python

I'm stuck on something that should probably be simple. I'm encountering an issue with Django signals while attempting to update a related model after saving an instance. I'm using Django 3.2 and have two models, `Author` and `Book`, where an author can have multiple books. I want to update a field in the `Author` model whenever a new `Book` is created. I connected a signal to the `post_save` event of the `Book` model, but it seems that the signal is fired multiple times, leading to unexpected behavior. Here's my code: ```python from django.db import models from django.db.models.signals import post_save from django.dispatch import receiver class Author(models.Model): name = models.CharField(max_length=100) book_count = models.IntegerField(default=0) class Book(models.Model): title = models.CharField(max_length=100) author = models.ForeignKey(Author, on_delete=models.CASCADE) @receiver(post_save, sender=Book) def update_author_book_count(sender, instance, created, **kwargs): if created: instance.author.book_count += 1 instance.author.save() ``` I expected the `book_count` to increment by 1 every time a book is created, but instead, it seems to increment multiple times for a single book creation. I checked for any recursive calls in my code but didn't find any. I also verified that an instance of `Book` is created only once when I run the following: ```python new_book = Book.objects.create(title='New Book', author=my_author) ``` However, when I print the `book_count` after the signal execution, it shows a count greater than expected. I'm wondering if there's a way to ensure that the signal executes only once per `Book` instance creation. Any insights or recommendations would be greatly appreciated! I'm working on a service that needs to handle this. Any help would be greatly appreciated!