👀 Views: 81 💬 Answers: 1 📅 Created: 2025-09-06

django query many-to-many Python

I've encountered a strange issue with I need some guidance on While developing a Django application to manage a bookstore, I need to filter books based on their associated authors..... I have a `Book` model and an `Author` model with a many-to-many relationship. The goal is to query all books that are authored by a specific author and also belong to a certain genre. Here are my models: ```python from django.db import models class Author(models.Model): name = models.CharField(max_length=100) class Genre(models.Model): name = models.CharField(max_length=100) class Book(models.Model): title = models.CharField(max_length=200) authors = models.ManyToManyField(Author) genre = models.ForeignKey(Genre, on_delete=models.CASCADE) ``` In the view, I'm attempting to filter books like this: ```python from django.shortcuts import render from .models import Book, Author def books_by_author_and_genre(request, author_id, genre_id): books = Book.objects.filter(authors__id=author_id, genre__id=genre_id) return render(request, 'books_list.html', {'books': books}) ``` However, when I invoke this view using a valid `author_id` and `genre_id`, it returns an empty queryset even though there are matching records in the database. I've confirmed the IDs exist in the database with these queries in the Django shell: ```python from myapp.models import Book, Author, Genre Author.objects.get(id=author_id) Genre.objects.get(id=genre_id) ``` Additionally, I added some debug prints to ensure I'm getting the correct IDs: ```python print(f'Author ID: {author_id}, Genre ID: {genre_id}') ``` I'm unsure if my filter logic is correct or if there's something else I might be missing. What could be causing the empty result set? Any insights would be greatly appreciated! For context: I'm using Python on Windows. Thanks, I really appreciate it! I'm developing on Ubuntu 20.04 with Python. What are your experiences with this?