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))