How to autocomplete ForeignKey field in admin?

Question

Django

The following models are available:

class Seller(models.Model):
    user_seller = models.ForeignKey(User, blank=True, null=True)
    
    def __str__(self):
        return self.user_seller.get_username()


class Item(models.Model):
    user = models.ForeignKey(Seller, blank=True, null=True)
    # Тут другие поля

    def __str__(self):
        return self.item_name

In the Django admin, you need to make sure that when you add an Item, user is automatically set based on the user. Those. the mechanism is as follows: admin (superuser) in the admin panel adds a Seller, after which this Seller can add an Item, and the user field for each Item should be set automatically based on the Seller's data, which adds the Item.
Tried to do like this:

def save_model(self, request, obj, form, change):
      if form.is_valid():
        obj.user = Seller.objects.filter(user_seller = request.user)
        obj.save()

To which Django told me that "Item.user" must be a "Seller" instance. And to tell you the truth, I don't really understand why this error occurs.
PS I'm just starting to learn Django, so don't kick too hard for stupid questions.

Answer 1

You need to write
filter() returns not a single object, but a collection of objects - QuerySet . The call to first() returns the first object in the collection, or None if it is empty.

Answer 2

I would write like this:

from django.contrib.auth.models import User

***

def save_model(self, request, obj, form, change):
      if form.is_valid():
        obj.user = request.user
        obj.save()