Python - asyncio - 从未检索到任务异常

Question

描述：（简化）

• 我有 2 个任务。
• 在每个任务中我有 3 个协程。
• 第一个任务的 2 个协程失败。（模拟）
• 在处理任务结果时，我收到一条“从未检索到任务异常”消息。
• 我相信这是因为该任务中仅处理了两个失败的协程之一的异常。
• 如何处理任务中两个协程的异常和/或避免“从未检索到任务异常”消息？

代码：（简体）

import asyncio
async def download(data):
    filename = "*" if data in ["b", "c"] else data  # simulated failure
    with open(filename, "w") as f:
        f.write(data)
async def coro(data_list):
    coroutines = [download(data) for data in data_list]
    for coroutine in asyncio.as_completed(coroutines):
        await coroutine
async def main():
    task1 = asyncio.create_task(coro(["a", "b", "c"]))
    task2 = asyncio.create_task(coro(["d", "e", "f"]))
    results = await asyncio.gather(task1, task2, return_exceptions=True)
    for _ in results:
        pass
asyncio.run(main())

输出：（简化）

Task exception was never retrieved
future: <Task finished coro=<download() done, defined at D:/myscript.py:2> exception=OSError(22, 'Invalid argument')>
Traceback (most recent call last):
  File "D:/myscript.py", line 4, in download
    with open(filename, "w") as f:
OSError: [Errno 22] Invalid argument: '*'

Answer 1

如果您想收集异常而不是引发异常，也可以使用asyncio.gather(return_exceptions=True)in coro。例如：

import asyncio

async def download(data):
    if data in ['b', 'c']:
        1/0    # simulate error
    return 42  # success

async def coro(data_list):
    coroutines = [download(data) for data in data_list]
    return await asyncio.gather(*coroutines, return_exceptions=True)

async def main():
    task1 = asyncio.create_task(coro(["a", "b", "c"]))
    task2 = asyncio.create_task(coro(["d", "e", "f"]))
    return await asyncio.gather(task1, task2, return_exceptions=True)

print(asyncio.run(main()))

这将打印：

[[42, ZeroDivisionError('division by zero'), ZeroDivisionError('division by zero')], [42, 42, 42]]