How to invoke `async` function from `cmd` (Python standard library, sync-async bridge, "coroutine ... was never awaited")?

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2

Following seems to work (without having tested extensively):

  • Keep all action callbacks of cmd.Cmd sync
  • Wrap every action callback by asyncio.run(run()), where run() is the async API function
  • asyncio.run() will be synchronously blocking, till async function completed.

A bit repetitive, as you need to do this for each action callback. That’s at least as good as I got it. Full example code:

import cmd
import asyncio

class MyShell(cmd.Cmd):
    def do_myaction(self, arg):
        async def run():
            await asyncio.sleep(3)
            print("Some app results")

        asyncio.run(run())


async def main():
    await asyncio.gather(shell(), other_task())
    print("Exiting...")


async def shell():
    def run():
        MyShell().cmdloop()

    # Run in separate thread to make interactive shell I/IO non-blocking
    await asyncio.to_thread(run)


async def other_task():
    # represents some concurrent initialization task
    await asyncio.sleep(1)
    print("Concurrent init task")


asyncio.run(main())