Python pipe in binary file from command line -u option

Is there a decoupled method of passing in a binary file without suffering the penalty of python having unbuffered stdout for the entire duration of running a program (if i intend to use only cmdline and not open(...,'rb')? It seems like -u is the only way to read in a file as binary data (from cmdline)

http://docs.python.org/using/cmdline.html

-u Force stdin, stdout and stderr to be totally unbuffered. On systems where it matters, also put stdin, stdout and stderr in binary mode.

You could perhaps avoid Python's file mode by instead grabbing the fileno out of the sys.stdin file-like object, and using os.read() to grab data from it?

import os
import sys

stdin_no = sys.stdin.fileno()
some_bytes = os.read(stdin_no, 1024)

This code will change standard input (only) to unbuffered mode. Using this you will not need to invoke the interpreter with -u. Unix only.

import fcntl, os, sys

def set_fd_nonblocking(fd):
  u"put an open file descriptor into non-blocking I/O mode"
  if fcntl.fcntl(fd, fcntl.F_SETFL, os.O_NONBLOCK) != 0:
    raise IOError, "can't set file descriptor %s option O_NONBLOCK" % (fd,)

set_fd_nonblocking(sys.stdin.fileno())

However I am unsure what side effects this could have, for example on the raw_input built-in function.

Be careful; even in non-blocking mode, if select tells you the fd is ready to read you will still need to catch OSError and check for e.errno == os.errno.EAGAIN. Such errors should be ignored.