Async/Await in Practice

Asyncio Core

Async/Await Crash Course

Coroutines let you write sequential-looking code that cooperatively multitasks.

Structure async codeGather tasks

Structure

import asyncio

async def fetch_order(order_id):
    await asyncio.sleep(0.1)
    return {'id': order_id}

async def main():
    order = await fetch_order('123')
    print(order)

asyncio.run(main())

• async declares coroutines; await pauses until awaited tasks complete.
• Use asyncio.run to bootstrap top-level coroutines.

Gathering tasks

orders = await asyncio.gather(
    fetch_order('123'),
    fetch_order('456'),
    fetch_order('789'),
    return_exceptions=True,
)

• asyncio.gather waits for all tasks; pass return_exceptions=True to avoid cancellation.
• asyncio.create_task schedules background work; keep references so you can await or cancel later.

Error handling

• Wrap awaits in try/except just like synchronous code.
• Use asyncio.TimeoutError with asyncio.wait_for to enforce deadlines.
• Cancel tasks with task.cancel() to clean up when shutting down.

Next up in your learning path

aiohttp

Apply async to HTTP clients/servers.

Practical

threading vs async

Revisit the comparison when building real apps.

Decision

Event loop internals

Deepen your understanding of scheduling.

Concept