how to use reverse query data from a child model to do arithmetic's in parent model?

from django.db import models


class location(models.Model):
name=models.CharField(max_length=100)
total_amount_spent=models.FloatField(default=0)
def __str__(self):
return self.name

class transaction(models.Model):
location_name=models.ForeignKey(location,on_delete=models.CASCADE,null=True)
date_time=models.DateTimeField(null=True)
amount=models.FloatField(null=True)
def __int__(self):
return self.id









I have created a model location, and a model transaction which has a many to one relation with location which has the information of a transaction done at a particular location, say 3 dollars spent at macdonalds, now I want to find all the transactions related to a particular location and add the amount to find the total amount spent,please help

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