How to perform operation on flask-admin database columns to store results in other column of same table - flask-sqlalchemy

Question

I am building flask admin app where I need to store total of couple of integer columns into third column of same table.
from flask_sqlalchemy import SQLAlchemy
from flask_admin.contrib.sqla import ModelView
from flask import Flask
import os
from flask_admin import Admin
application = Flask(__name__)
project_dir = os.path.dirname(os.path.abspath(__file__))
database_file = "sqlite:///{}".format(os.path.join(project_dir,"testing.db"))
application = Flask(__name__)
application.config["SQLALCHEMY_DATABASE_URI"] = database_file
application.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
application.secret_key = "ssshhhh"
db = SQLAlchemy(application)
admin = Admin(application,name="FLASK")
class Test(db.Model):
id = db.Column("ID",db.Integer,primary_key=True)
first_no = db.Column("First_no",db.Integer)
second_no = db.Column("Second_no",db.Integer)
total = db.Column("Total",db.Integer)
class TestView(ModelView):
page_size = 20
edit_modal = True
if __name__ == '__main__':
db.create_all()
admin.add_view(TestView(Test, db.session))
application.run(debug=True)
Above example let me store values in all three fields manually which is not expected.
Expected result that I am looking for get total of couple of integers and stores in database as well.

Answer 1

Two options you can use:
Use the onupdate parameter of Column to set the value of total on update, for example:
total = db.Column("Total", db.Integer, onupdate=first_no + second_no)
Use a hybrid_property to calculated the total without storing the value:
class Test(db.Model):
...
#hybrid_property
def total(self):
return self.first_no + self.second_no