sample_program.py

(source below)
#!/usr/bin/env python

"""
A sample program.
"""

# built-in
from contextlib import suppress
import os
import sys
import time


def main(argv: list[str]) -> int:
    """A sample program entry."""

    # CLI arguments not currently used.
    print("arguments: " + ", ".join(argv), flush=True)

    # Enable polling read.
    os.set_blocking(sys.stdin.fileno(), False)

    keep_going = True
    idx = 0

    with suppress(KeyboardInterrupt):
        while keep_going:
            time.sleep(0.5)

            print(f"stdout message ({idx})", flush=True)
            print(f"stderr message ({idx})", file=sys.stderr, flush=True)

            data = sys.stdin.buffer.read()
            if data is not None:
                if not data:
                    keep_going = False
                    msg = "got eof - exiting"
                else:
                    msg = f"got stdin: '{data.decode().rstrip()}'"

                print(msg, flush=True)
                print(msg, file=sys.stderr, flush=True)

            idx += 1

    # Use an arbitrary return value.
    return idx % 64


if __name__ == "__main__":
    sys.exit(main(sys.argv))