How can I use SQLAlchemy with async in Python?

How can I use SQLAlchemy with async in Python?

You can use SQLAlchemy with async by utilizing the asyncio library along with the asyncpg driver for PostgreSQL.

Can you show me a simple example of an async query?

Sure! Here's a basic example:

import asyncio
from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession
from sqlalchemy.orm import sessionmaker

DATABASE_URL = 'postgresql+asyncpg://user:password@localhost/dbname'

engine = create_async_engine(DATABASE_URL, echo=True)
AsyncSessionLocal = sessionmaker(bind=engine, class_=AsyncSession)

async def async_main():
    async with AsyncSessionLocal() as session:
        result = await session.execute('SELECT * FROM my_table')
        for row in result:
            print(row)

asyncio.run(async_main())

What if I want to use it with FastAPI?

You can integrate SQLAlchemy async with FastAPI by using dependency injection. Here's a quick example:

from fastapi import FastAPI, Depends
from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine
from sqlalchemy.orm import sessionmaker

app = FastAPI()

DATABASE_URL = 'postgresql+asyncpg://user:password@localhost/dbname'
engine = create_async_engine(DATABASE_URL, echo=True)
AsyncSessionLocal = sessionmaker(bind=engine, class_=AsyncSession)

async def get_db() -> AsyncSession:
    async with AsyncSessionLocal() as session:
        yield session

@app.get('/items/')
async def read_items(db: AsyncSession = Depends(get_db)):
    result = await db.execute('SELECT * FROM items')
    return result.fetchall()

Are there any performance considerations I should be aware of?

Yes, when using async with SQLAlchemy, ensure that your database can handle concurrent connections efficiently. Also, avoid blocking calls within async functions.