How to Count the Number of Objects in a ManyToManyField in Django

In this article, we show how to count the number of objects in a ManyToManyField in Django.

A ManyToManyField in Django is a field that allows multiple objects to be stored. This is useful and applicable for things such as shopping carts, where a user can buy multiple products.

To add an item to a ManyToManyField, we can use the add() function. To remove an item from a ManyToManyField, we can use the remove() function.

But how do we count the number of objects in a ManyToManyField?

Let's say we have the following model shown below.

# models.py file class ShoppingCart(models.Model): user= models.OneToOneField(User) products= models.ManyToManyField(Product, blank=True)

So in the models.py file, above, we have a model, ShoppingCart, that contains 2 fields, with the products row being a ManyToManyField.

Now how do we count the number of objects in this ManyToManyField?

We show this in the following code in the views.py file.

# views.py file from .models import ShoppingCart shoppingcartuser= ShoppingCart.objects.get(user= request.user) itemscount= shoppingcartuser.products.all().count()

So in this code, we have to import the model, ShoppingCart, because this is the model that contains the ManyToManyField we are trying to retrieve the items from.

So each ShoppingCart contains a user. We select the user (the row) of data we want to deal with and get this row. We can then retrieve all of the items from the ManyToManyField, products, from this row.

We retrieve all of the objects from the ManyToManyField, products, using the line, shoppingcartitems= shoppingcartuser.products.all() If we add, .count(), to the end of this, we are able to get the count of all of the objects in the ManyToManyField.

template File

Lastly, we just have the template file to render.

So we pass that variable into the context dictionary and then we have it in the templates file.

This is shown below.

# template file Number of Items in Shopping Cart: {{itemscount}}

So this is how we can count the number of objects in a ManyToManyField in Django.

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