pythonasynchronousasync-awaittaskpython-asyncio

Any difference between await asyncio.Task and asyncio.Task.result()?

After the task already completed, is there any difference between await asyncio.Task and asyncio.Task.result()?

The only difference in the following code is how I read the value in task.

import asyncio
from asyncio import TaskGroup

async def func():
    await asyncio.sleep(2)
    return 0

async def main():
    async with TaskGroup() as tg:
        task = tg.create_task(func())
        print(await task)

asyncio.run(main())

vs

import asyncio
from asyncio import TaskGroup

async def func():
    await asyncio.sleep(2)
    return 0

async def main():
    async with TaskGroup() as tg:
        task = tg.create_task(func())
    # The await is implicit when the context manager exits.
    print(task.result())

asyncio.run(main())

Which code is the preferred one?

Solution

  • The source code snippet below shows that await task ends up calling task.result() if the task is done. So the answer is: no difference in this case.

        def __await__(self):
        if not self.done():
            self._asyncio_future_blocking = True
            yield self  # This tells Task to wait for completion.
        if not self.done():
            raise RuntimeError("await wasn't used with future")
        return self.result()  # May raise too.

# location: asyncio/futures.py, in class _Future,
# the Task class is derived from it