[Python] Django - how to order queryset for varying query?

I have this issue where I want to order my queryset according to a compute value based on a query in descending order.

Query: ?fruit=Apple&?fruit=Pear

In this case:

Num. Apples + Num. Pears + (Num. Apples * Num. Pears)


models.py

class Customer(BaseModel):
name = models.CharField('name'), max_length=255, blank=True
fruits = models.JsonField('fruit'), null=True, blank=True, default=dict)


My Customer.fruits looks something like this:

fruits = { name: Apple, count: 10 },
{ name: Pear, count: 4 },
{ name: Cherry, count: 1 },
{ name: Avocado, count: 2 }


views.py:

def get_queryset(self):
fruits = dict(self.request.GET).get('fruit', [])
queryset = Customers.objects.all()
if fruits:
queryset = sorted(queryset, reverse = True, key=lambda customer: self.calculate_order(customer, fruits))
return queryset

def calculate_order(self, customer, fruits):
value_list = [fruit['count'] for fruit in customer.fruits if fruit['name'] in fruits]
return sum(value_list) + (reduce((lambda x, y: x*y), value_list)) if value_list else 0


This seems to be ordering the data correctly from what I have tested so far, however doesn't seem like the best way to do it.

Is there a better way using Django Queryset API for ordering this data? Since the way it's ordering now is a bit time consuming since I have to iterate on all the records on the database.

Edit: I have no problem with having another model for fruits.

class Customer(BaseModel):
name = models.CharField('name'), max_length=255, blank=True
fruits = models.ManytoManyField(Fruits, through='CustomerFruits')

class Fruits(BaseModel):
name = models.CharField('name'), max_length=255, blank=True
count = models.IntegerField('count'), null=True, blank=True


How can I order the customer information using this two models with the computed value?

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