Added SQLAlchemy Example

SQLAlchemy-ORM/demo.py

@@ -0,0 +1,26 @@
+"""Very quick introduction to python classes"""
+
+from typing import override
+
+
+class Food:
+    name: str
+    calories: int
+
+    count: int = 1
+
+    def __init__(self, name: str, calories: int) -> None:
+        self.name = name
+        self.calories = calories
+
+    @override
+    def __str__(self) -> str:
+        return f"A(n) {self.name} with {self.calories}"
+
+    @override
+    def __repr__(self) -> str:
+        return f"Food({self.name!r}, {self.calories!r})"
+
+
+apple = Food("apple", 100)
+pizza = Food("pizza", 300)

SQLAlchemy-ORM/quick_start.py

@@ -0,0 +1,117 @@
+"""Example code from the ORM Quick Start.
+
+https://docs.sqlalchemy.org/en/20/orm/quickstart.html
+"""
+
+from typing import override
+
+from sqlalchemy import ForeignKey, String, create_engine, select
+from sqlalchemy.orm import DeclarativeBase, Mapped, Session, mapped_column, relationship
+
+# ------------------------------------------------------------------------------
+# Declare Models
+# ------------------------------------------------------------------------------
+
+
+class Base(DeclarativeBase):
+    pass
+
+
+class User(Base):
+    __tablename__: str = "user_account"
+
+    id: Mapped[int] = mapped_column(primary_key=True)
+    name: Mapped[str] = mapped_column(String(30))
+    fullname: Mapped[str | None] = mapped_column(String, nullable=True)
+
+    addresses: Mapped[list["Address"]] = relationship(
+        back_populates="user", cascade="all, delete-orphan"
+    )
+
+    @override
+    def __repr__(self) -> str:
+        return f"User(id={self.id!r}, name={self.name!r}, fullname={self.fullname!r})"
+
+
+class Address(Base):
+    __tablename__: str = "address"
+
+    id: Mapped[int] = mapped_column(primary_key=True)
+    email_address: Mapped[str] = mapped_column(String, nullable=True)
+    user_id: Mapped[int] = mapped_column(ForeignKey("user_account.id"))
+
+    user: Mapped["User"] = relationship(back_populates="addresses")
+
+    @override
+    def __repr__(self) -> str:
+        return f"Address(id={self.id!r}, email_address={self.email_address!r})"
+
+
+# ------------------------------------------------------------------------------
+# Create an Engine / Emit CREATE TABLE DDL
+# ------------------------------------------------------------------------------
+
+engine = create_engine("sqlite://", echo=True)
+
+Base.metadata.create_all(engine)
+
+# ------------------------------------------------------------------------------
+# Create Objects and Persist
+# ------------------------------------------------------------------------------
+
+with Session(engine) as session:
+    spongebob = User(
+        name="spongebob",
+        fullname="Spongebob Squarepants",
+        addresses=[Address(email_address="spongebob@sqlalchemy.org")],
+    )
+    sandy = User(
+        name="sandy",
+        fullname="Sandy Cheeks",
+        addresses=[
+            Address(email_address="sandy@sqlalchemy.org"),
+            Address(email_address="sandy@squirrelpower.org"),
+        ],
+    )
+    patrick = User(name="patrick", fullname="Patrick Star")
+    session.add_all([spongebob, sandy, patrick])
+    session.commit()
+
+# ------------------------------------------------------------------------------
+# Simple SELECT / SELECT with JOIN
+# ------------------------------------------------------------------------------
+
+session = Session(engine)
+
+stmt = select(User).where(User.name.in_(["spongebob", "sandy"]))
+for user in session.scalars(stmt):
+    print(user)
+
+stmt = (
+    select(Address)
+    .join(Address.user)
+    .where(User.name == "sandy")
+    .where(Address.email_address == "sandy@sqlalchemy.org")
+)
+sandy_address = session.scalars(stmt).one()
+print(sandy_address)
+
+# ------------------------------------------------------------------------------
+# Make Changes / Some Deletes
+# ------------------------------------------------------------------------------
+
+stmt = select(User).where(User.name == "patrick")
+patrick = session.scalars(stmt).one()
+
+patrick.addresses.append(Address(email_address="patrickstar@sqlalchemy.org"))
+sandy_address.email_address = "sandy_cheeks@sqlalchemy.org"
+
+session.commit()
+
+sandy = session.get(User, 2)
+assert sandy is not None
+sandy.addresses.remove(sandy_address)
+
+session.flush()
+session.delete(patrick)
+session.commit()

devenv.nix

@@ -11,9 +11,12 @@
       enable = true;
       requirements = ''
         Faker==37.8.0
+        greenlet==3.2.4
         psycopg==3.2.10
         psycopg-binary==3.2.10
         python-dotenv==1.1.1
+        SQLAlchemy==2.0.44
+        typing_extensions==4.15.0
         tzdata==2025.2
       '';
     };