How to use SQLAlchemy with numerical enums?

sqla-numerical-enum.py

# /// script
# requires-python = ">=3.14"
# dependencies = [
#     "sqlalchemy==2.0.48",
#     "starlette-admin==0.16.0",
#     "uvicorn==0.41.0",
# ]
# ///
"""
How to use SQLAlchemy with numerical enums?

`IntEnum` class is taken from this article: [Using Python enums in SQLAlchemy models](https://michaelcho.me/article/using-python-enums-in-sqlalchemy-models/), all credits to the author.
"""

import datetime
import enum

import uvicorn
from sqlalchemy import Integer
from sqlalchemy import TypeDecorator
from sqlalchemy import create_engine
from sqlalchemy.orm import DeclarativeBase
from sqlalchemy.orm import Mapped
from sqlalchemy.orm import mapped_column
from starlette.applications import Starlette
from starlette_admin.contrib.sqla import Admin
from starlette_admin.contrib.sqla import ModelView
from starlette_admin.fields import EnumField

engine = create_engine(
    "sqlite:///db.sqlite3", connect_args={"check_same_thread": False}
)


class IntEnum(TypeDecorator):
    """
    Enables passing in a Python enum and storing the enum's *value* in the db.
    The default would have stored the enum's *name* (ie the string).
    """

    impl = Integer

    def __init__(self, enumtype, *args, **kwargs):
        super(IntEnum, self).__init__(*args, **kwargs)
        self._enumtype = enumtype

    def process_bind_param(self, value, dialect):
        if isinstance(value, int):
            return value

        return value.value

    def process_result_value(self, value, dialect):
        return self._enumtype(value)


class Gender(enum.IntEnum):
    MALE = 1
    FEMALE = 2
    PREFER_NOT_TO_SAY = 3


class Base(DeclarativeBase):
    pass


class Mixin:
    id: Mapped[int] = mapped_column(
        primary_key=True,
        autoincrement=True,
        index=True,
        unique=True,
    )
    date_created: Mapped[datetime.datetime] = mapped_column(
        default=datetime.datetime.utcnow,
        index=True,
    )
    date_updated: Mapped[datetime.datetime] = mapped_column(
        default=datetime.datetime.utcnow,
        onupdate=datetime.datetime.utcnow,
        index=True,
    )


class Person(Base, Mixin):
    __tablename__ = "person"
    name: Mapped[str]
    gender: Mapped[Gender] = mapped_column(IntEnum(Gender))


class PersonView(ModelView):
    fields = [
        "name",
        EnumField(
            name="gender",
            coerce=int,
            choices=[
                (1, "Male"),
                (2, "Female"),
                (3, "Perefer not to say"),
            ],
        ),
    ]


def main() -> None:
    with engine.connect() as conn:
        person = Person(name="John Doe", gender=1)
        conn.add(person)
        conn.commit()
    Base.metadata.create_all(engine)

    app = Starlette()
    admin = Admin(engine, title="SQLAlchemy Numerical Enum Example")
    admin.add_view(PersonView(Person))
    admin.mount_to(app)

    uvicorn.run(app, host="127.0.0.1", port=8000)


if __name__ == "__main__":
    main()

for the ones want to do with Column, I did this way;

gender = Column(IntEnum(Gender), name="gender", nullable=False)

note: nullable is optional