L6·Expert

⚡async / await & Event Loop

Cooperative concurrency for I/O-bound work.

asyncawaitasynciocoroutine

§ 1Coroutines

async def creates a coroutine function. Calling it returns a coroutine object — nothing runs until you await or schedule it.

§ 2Event loop

asyncio.run(main()) starts a loop. Await points let other tasks progress while you wait on I/O.

§ 3Gather

asyncio.gather(*coros) runs them concurrently and returns results in order.

Example

1import asyncio
2
3async def fetch(name, delay):
4    await asyncio.sleep(delay)
5    return f"{name} done"
6
7async def main():
8    results = await asyncio.gather(
9        fetch("A", 0.3),
10        fetch("B", 0.1),
11        fetch("C", 0.2),
12    )
13    print(results)
14
15asyncio.run(main())

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Checkpoint quiz

Question 1 / 2

Is async/await good for CPU-bound work?

JSON & Serialization

Threads, Processes & the GIL