What is async context manager for database transactions?

Question

Accepted Answer

**Async context managers** manage **database transactions** automatically.

```python
from sqlalchemy.ext.asyncio import AsyncSession
from contextlib import asynccontextmanager

# SQLAlchemy async session
async def get_db():
    async with AsyncSession(engine) as session:
        try:
            yield session
            await session.commit()
        except Exception:
            await session.rollback()
            raise

# Custom transaction manager
@asynccontextmanager
async def transaction(session: AsyncSession):
    async with session.begin():
        yield session
    # Auto-commits on success, rollbacks on exception

# Usage
async def transfer_money(from_id, to_id, amount):
    async with get_db() as db:
        sender = await db.get(Account, from_id)
        receiver = await db.get(Account, to_id)
        sender.balance -= amount
        receiver.balance += amount
        # Auto-commits when exiting context

async def main():
    await transfer_money(1, 2, 100)

asyncio.run(main())
```

**Benefits:**
- Automatic commit/rollback.
- Exception safety.
- Clean resource management.

Python: What is async context manager for database transactions?