While importing csv entries to a database: How can I update the db IF a duplicate csv entry is found?

def add_csv():
    with open('inventory.csv') as csvfile:
        data = csv.reader(csvfile)
        next(data)
        for row in data:
            product_in_db = session.query(Product).filter(
                Product.product_name == row[0]).one_or_none()
            if product_in_db == None:
                product_name = row[0]
                product_price = clean_price(row[1])
                product_quantity = clean_quantity(row[2])
                date_updated = clean_date_updated(row[3])
                new_product = Product(product_name=product_name, product_price=product_price,
                                      product_quantity=product_quantity, date_updated=date_updated)
                session.add(new_product)
#Note: This is where the code begins dealing with a duplicate value.
            elif product_in_db == True:
                if product_in_db.date_updated < new_product.date_updated:
                    session.add(new_product)
                    session.delete(product_in_db)
                elif product_in_db.date_updated > new_product.date_updated:
                    pass
        session.commit()

from sqlalchemy import (create_engine, Column,
                        Integer, String, DateTime)
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker


engine = create_engine('sqlite:///inventory.db', echo=False)
Session = sessionmaker(bind=engine)
session = Session()
Base = declarative_base()


class Product(Base):
    __tablename__ = "products"
    product_id = Column(Integer, primary_key=True)
    product_name = Column("Product Name", String)
    product_price = Column("Product Price", Integer)
    product_quantity = Column("Product Quantity", Integer)
    date_updated = Column("Date Updated", DateTime)

    def __repr__(self):
        return f'Name: {self.product_name}, Quantity: {self.product_quantity}, Price: {self.product_price}, Date Updated: {self.date_updated}'


if __name__ == "__main__":
    Base.metadata.create_all(engine)