python-sqlalchemy

# SQLAlchemy ORM Patterns Modern SQLAlchemy 2.0+ patterns for database access in Python applications. ## Model Definition ```python from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column from sqlalchemy import String from uuid import UUID from decimal import Decimal class Base(DeclarativeBase): pass class ProductModel(Base): __tablename__ = "products" id: Mapped[UUID] = mapped_column(primary_key=True) name: Mapped[str] = mapped_column(String(100)) price: Mapped[Decimal] in_stock: Mapped[bool] = mapped_column(default=True) ``` ## Session Management ```python from sqlalchemy import create_engine from sqlalchemy.orm import sessionmaker engine = create_engine("postgresql://user:pass@localhost/db") SessionLocal = sessionmaker(bind=engine) def get_db(): db = SessionLocal() try: yield db finally: db.close() ``` ## Query Patterns ```python # Select stmt = select(ProductModel).where(ProductModel.price > 100) products = session.execute(stmt).scalars().all() # Filter products = session.query(ProductModel).filter(ProductModel.in_stock == True).all() # Get by ID product = session.get(ProductModel, product_id) # Count count = session.query(ProductModel).count() ``` ## Upsert ```python from sqlalchemy.dialects.postgresql import insert stmt = insert(ProductModel).values( id=product_id, name="Widget", price=9.99, ) # On conflict, update stmt = stmt.on_conflict_do_update( index_elements=["id"], ...