asyncio：让协程任务可以并发、超时和取消

import asyncio


async def fetch(name: str, delay: float) -> str:
    print(f"start {name}")
    try:
        await asyncio.sleep(delay)
        return f"done {name}"
    finally:
        print(f"cleanup {name}")


async def main() -> None:
    fast = asyncio.create_task(fetch("fast", 0.2))
    slow = asyncio.create_task(fetch("slow", 2.0))

    print(await fast)
    try:
        print(await asyncio.wait_for(slow, timeout=0.5))
    except TimeoutError:
        print("slow timed out")


if __name__ == "__main__":
    asyncio.run(main())

async def call_blocking(argument: str) -> str:
    return await asyncio.to_thread(blocking_function, argument)

import asyncio


async def limited_work(name: str, semaphore: asyncio.Semaphore) -> str:
    async with semaphore:
        await asyncio.sleep(0.1)
        return name


async def run_batch() -> list[str]:
    semaphore = asyncio.Semaphore(3)
    jobs = [limited_work(str(index), semaphore) for index in range(10)]
    return await asyncio.gather(*jobs)


if __name__ == "__main__":
    print(asyncio.run(run_batch()))