Question

I have a few model classes with basic one-to-many relationships. For example, a book has many recipes, and each recipe has many ingredients:

class Book(models.Model):     name = models.CharField(max_length=64)  class Recipe(models.Model):     book = models.ForeignKey(Book)     name = models.CharField(max_length=64)  class Ingredient(models.Model):     text = models.CharField(max_length=128)     recipe = models.ForeignKey(Recipe) 

I’d like a flat list of all ingredients in all recipes from a particular book. What’s the best way to express this in Python?

If I was using LINQ, I might write something like this:

var allIngredients = from recipe in book.Recipes                      from ingredient in recipe.Ingredients                      select ingredient; 

Answer 1

Actually, it looks like there’s a better approach using filter:

my_book = Book.objects.get(pk=1) all_ingredients = Ingredient.objects.filter(recipe__book=my_book)