#2 was an old misunderstanding by me about file.read() vs. os.read() w.r.t pipes, so is not needed.

As for returning the status code vs the pid, it looks like spawn() is designed to return only when it can't read/write to the subprocess.  You could return the pid at this point, but the process has most likely finished running at this point so the only thing you'd be likely to do is call waitpid() on it (and it is necessary to call waitpid() for the child process to be cleaned up properly).

That's why I suggested that pty.spawn() get the child status itself.