# 项目文件：demos/task_group_results.py
# async with 离开前等待组内任务结束，之后 result 读取已完成的值。
import asyncio


async def twice(value):
    await asyncio.sleep(0)
    return value * 2


async def main():
    async with asyncio.TaskGroup() as group:
        tasks = [group.create_task(twice(value)) for value in [20, 35, 45]]
    print([task.result() for task in tasks])


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

# 项目文件：demos/task_group_failure.py
# 等待项启动后，另一个任务才抛错；任务组取消等待项，等 finally 完成后向外报告。
import asyncio


async def waiting(ready, trace):
    try:
        trace.append("等待项开始")
        ready.set()
        await asyncio.Event().wait()
    finally:
        trace.append("等待项收尾")


async def failing(ready, trace):
    await ready.wait()
    trace.append("失败项抛错")
    raise ValueError("书目格式错误")


async def main():
    ready, trace = asyncio.Event(), []
    try:
        async with asyncio.TaskGroup() as group:
            group.create_task(waiting(ready, trace))
            group.create_task(failing(ready, trace))
    except* ValueError as errors:
        print("收到错误", [str(error) for error in errors.exceptions])
    print(trace)


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

# 项目文件：demos/gather_errors.py
# return_exceptions=True 保留各项结果；调用者逐项决定如何显示或继续处理。
import asyncio


async def check_minutes(value):
    await asyncio.sleep(0)
    if value < 0:
        raise ValueError("分钟数为负")
    return value * 2


async def main():
    results = await asyncio.gather(
        check_minutes(20), check_minutes(-1), return_exceptions=True
    )
    for result in results:
        if isinstance(result, Exception):
            print("错误", result)
        else:
            print("结果", result)


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