I’m trying to find a way to convert dataclass fields both pre and post SQLAlchemy queries.

Let’s say I have this table:

create table Products (
    id bigint primary key not null,
    productName text,
    productPrice bigint
);

And then let’s say that this dataclass is used to represent the table.

from decimal import *
from dataclasses import dataclass

from sqlalchemy import Table, Column, Integer, String
from sqlalchemy.orm import registry

mapper_registry = registry()

@mapper_registry.mapped
@dataclass
class Product():
    __table_args__ = {'quote':False}

    __table__ = Table(
        "Products",
        mapper_registry.metadata,
        Column("id", Integer, primary_key=True),
        Column("productName", String),
        Column("productPrice", Integer),
    )

    id: int = 0
    productName: str = ''
    productPrice: Decimal = Decimal('0')

In my tables I use a bigint to represent the currency while in the dataclass I want it represented as Decimal. So ideally, when I use SQLAlchemy to insert a new product the productPrice will be converted to int by multiplying it by 100 and then casting while on select operations, the column should be divided by 100 and casted back to Decimal.

I don’t believe __post_init__ will fully solve my problem so I’m not sure this is possible in Python and maybe instead something that can be done within Postgres itself?