Possible mis-leading sample code in Doc/library/asyncio-task.rst

[galmyk]

In the Coroutines and Tasks, there is a possible semantic bug in one of sample codes.

In the Awaitables subsection, the sample code for coroutines is:

import asyncio

async def nested():
    return 42

async def main():
    # Nothing happens if we just call "nested()".
    # A coroutine object is created but not awaited,
    # so it *won't run at all*.
    nested()

    # Let's do it differently now and await it:
    print(await nested())  # will print "42".

asyncio.run(main())

The code and its comments are all correct. But think about these two lines:

• in line 10: nested()
• in line 13: print(await nested())

Since nested function doesn't print anything and just returns an integer number, if code in line 10 has no bug at all (even related to asyncio/async/await things), it prints nothing.

So I think, it is better to move the print to nested function and change the code sample to:

import asyncio

async def nested():
    print(42)

async def main():
    # Nothing happens if we just call "nested()".
    # A coroutine object is created but not awaited,
    # so it *won't run at all*.
    nested()  # will raise RuntimeWarning: coroutine 'nested' was never awaited

    # Let's do it differently now and await it:
    await nested()  # will print "42".

asyncio.run(main())

Linked PRs

• gh-125289: Update sample code in asyncio-task.rst #125292
• [3.13] gh-125289: Update sample code in asyncio-task.rst (GH-125292) #125374
• [3.12] gh-125289: Update sample code in asyncio-task.rst (GH-125292) #125375

[JelleZijlstra]

I agree your proposed change would make the example clearer. Feel free to submit a PR!