> Also, Richard Oudkerk's claims above about not needing to use fcntl to swap flags is not correct. It's necessary to not block on reading, even if select is used. Select just guarantees that there is at least 1 byte or a closed handle, not that your full read will complete.

On Linux, `fcntl` is not necessary if you use `os.read(pipe, bufsize)` after `select` instead of `pipe.read(bufsize)`. `os.read` may just return less than `bufsize` bytes if they are not available.