Kristján, thank you for the response.  The socket communication part of IDLE is pretty much a black box to me.  Just to clarify, you are saying that select polling is only needed for non-blocking sockets; sockets are blocking by default; and you see no override of the default.  Me neither.  It would be nice to know.  Idlelib.PyShell has the following lines: 
<445>        self.rpcclt.listening_sock.settimeout(10)
<561>            response = clt.pollresponse(self.active_seq, wait=0.05)
The wait is ultimately passed to rpc.py, line 353:
            r, w, x = select.select([self.sock.fileno()], [], [], wait)

(IDLE is very much in use, and I hope to modernize the 3.x version, and perhaps replace the sockets with non-blocking use of pipes.)

Michael: I cannot change 2.7.5 and I am not inclined to change 2.7.12+ until I know there is a problem with the current 2.7 release.  Numerous people are using IDLE with 2.7.11 (and 3.x) on Windows without problems.