From b82833ebde76e3f886c242b7b49f59d1b6038afa 2015-01-24 00:42:41
From: Thomas Kluyver <takowl@gmail.com>
Date: 2015-01-24 00:42:41
Subject: [PATCH] Merge pull request #7560 from minrk/no-displayhook-no-data

don't send empty execute_result messages
---

diff --git a/IPython/kernel/zmq/displayhook.py b/IPython/kernel/zmq/displayhook.py
index 651d03c..9776ef4 100644
--- a/IPython/kernel/zmq/displayhook.py
+++ b/IPython/kernel/zmq/displayhook.py
@@ -68,6 +68,7 @@ class ZMQShellDisplayHook(DisplayHook):
         """Finish up all displayhook activities."""
         sys.stdout.flush()
         sys.stderr.flush()
-        self.session.send(self.pub_socket, self.msg, ident=self.topic)
+        if self.msg['content']['data']:
+            self.session.send(self.pub_socket, self.msg, ident=self.topic)
         self.msg = None