sets file to nonblocked state. sets process's stdout/stderr to nonblocked state too.

unblock.py

def unblock(f):
  """
    sets file to nonblocked state.  sets process's stdout/stderr to nonblocked state too.
  """
  from subprocess import Popen
  if type(p)==Popen:
    unblock(p.stderr)
    unblock(p.stdout)
    return
  import os,fcntl
  # get the file descriptor
  fd = f.fileno()
  # get the file's current flag settings                                      
  fl = fcntl.fcntl(fd, fcntl.F_GETFL)
  # update the file's flags to put the file into non-blocking mode.           
  fcntl.fcntl(fd, fcntl.F_SETFL, fl | os.O_NONBLOCK)
  pass