how to get non-blocking file descriptors from a popen?

[Donn Cave]

Quoth "Gregory P. Smith" <gsmith-mysterymeat at mysterymeat-transmeta.com>:
| Using os.popen (or better, popen2.Popen4 objects), how can I switch the 
| returned file objects to non-blocking io mode for appropriate use with 
| select.poll?

You know,
- select & poll really use a file "descriptor" - they'll accept various
  alternatives, but only when there's a callable fileno attribute to
  return the file descriptor.  And when you go that way, any input
  through a file object is liable to buffer up data that select can't
  see, so the file object is little or no use.  Use os.read() instead.
- when you use select, that file descriptor does _not_ need to be
  non-blocking.  select's whole purpose is to tell you when I/O will
  not block, so if you let it tell you when to read, non-blocking is
  irrelevant.

	Donn Cave, donn at u.washington.edu