[Python] Wrapping a python sub process

I would like to wrap an external process with a python subprocess to add a control on the input and output. I created a small wrapper program, and managed to change the input and output send to the internal process when I need it. I couldn't return output without calling the inner process - see the TODO inside my code

import asyncio
import sys


async def main(program: str, cmd_args):
process = await asyncio.create_subprocess_exec(
program,
*cmd_args.split(" "),
stdin=asyncio.subprocess.PIPE,
stdout=asyncio.subprocess.PIPE,
)

async def read_stdout():
while output := await process.stdout.readline():
sys.stdout.write(" " + output.decode("utf-8"))
sys.stdout.flush()

async def read_stdin():
while l := await asyncio.to_thread(sys.stdin.readline):
yield l.strip()

stdout_task = asyncio.create_task(read_stdout())

async for line in read_stdin():
if some_condition(line):
# TODO - return output without calling the inner process
pass
else:
process.stdin.write(line.encode("utf-8"))
process.stdin.write(b"\n")
await process.stdin.drain()

process.stdin.close()
await stdout_task
await process.wait()


if __name__ == "__main__":
asyncio.run(main(sys.argv[1], sys.argv[2]))

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