函数已使用await仍触发‘coroutine was never awaited’报错的技术咨询

Hey there! Let's break down why you're seeing that coroutine was never awaited error, even though you’ve got an await inside your aio_wrapper function.

The Root Cause #

Your _aio function returns an async wrapper (aio_wrapper). When you call self._aio(self._client.get_object)(Bucket=self.bucket_name, Key=key), you’re creating a coroutine object—but you never actually tell Python to run this coroutine by using await on it.

The await inside aio_wrapper handles the execution of loop.run_in_executor, but that’s entirely internal to the wrapper. The act of calling the async wrapper itself produces a coroutine that needs to be awaited to get the final result. If you check the type(res) in your current code, you’ll see it’s <class 'coroutine'>—that unexecuted coroutine is exactly what’s triggering the error.

Solutions #

1. Await the Coroutine in an Async Function #

If your calling code is part of an async context, simply add await when you invoke the wrapped function:

async def process_images():
    for key in image_keys:
        # Add await here to run the coroutine and retrieve the actual result
        res = await self._aio(self._client.get_object)(Bucket=self.bucket_name, Key=key)
        print(type(res))  # Now this will show the result type, not a coroutine

# Execute your async function
asyncio.run(process_images())

2. Batch Process with asyncio.gather (More Efficient) #

Since you’re processing multiple objects, using asyncio.gather to run all coroutines concurrently will be much faster than awaiting them one by one:

async def fetch_all_images():
    # Create a list of coroutine tasks
    tasks = [
        self._aio(self._client.get_object)(Bucket=self.bucket_name, Key=key)
        for key in image_keys
    ]
    # Run all tasks at once and wait for all results
    results = await asyncio.gather(*tasks)
    
    for res in results:
        print(type(res))

asyncio.run(fetch_all_images())

Key Takeaway #

Async functions return coroutines when called—you must always await those coroutines (or schedule them via an asyncio loop) to execute them. The await inside your wrapper handles a nested async operation, but it doesn’t replace the need to await the wrapper itself.

内容的提问来源于stack exchange，提问作者ziad_dp