ExceptionGroup and except* for Handling Multiple Exceptions

When multiple async tasks fail simultaneously via asyncio.TaskGroup, only the first exception was surfaced previously. Multiple concurrent failures were lost or required ugly workarounds.

Use ExceptionGroup and except* to handle multiple simultaneous exceptions.

import asyncio

async def failing_task(name: str, should_fail: bool) -> str:
    await asyncio.sleep(0.1)
    if should_fail:
        raise ValueError(f'{name} failed')
    return name

async def main():
    try:
        async with asyncio.TaskGroup() as tg:
            t1 = tg.create_task(failing_task('a', True))
            t2 = tg.create_task(failing_task('b', False))
            t3 = tg.create_task(failing_task('c', True))
        # t1 and t3 both fail — ExceptionGroup raised with both errors
    except* ValueError as eg:
        for exc in eg.exceptions:
            print(f'Caught: {exc}')
    except* TypeError as eg:
        print(f'Type errors: {eg.exceptions}')

# Manual ExceptionGroup
def process_all(items: list) -> None:
    errors = []
    for item in items:
        try:
            process(item)
        except Exception as e:
            errors.append(e)
    if errors:
        raise ExceptionGroup('Processing errors', errors)

asyncio.TaskGroup collects all task exceptions and raises them as an ExceptionGroup. The except* syntax filters ExceptionGroups by exception type, allowing each type to be handled separately.