flush stdout/stderr on displayhook

This helps stream output arrive before pyout.

closes gh-780

IPython/zmq/displayhook.py

@@ -1,68 +1,73 b''
 import __builtin__
+import sys
 from base64 import encodestring
 
 from IPython.core.displayhook import DisplayHook
 from IPython.utils.traitlets import Instance, Dict
 from session import extract_header, Session
 
 class ZMQDisplayHook(object):
     """A simple displayhook that publishes the object's repr over a ZeroMQ
     socket."""
     topic=None
 
     def __init__(self, session, pub_socket):
         self.session = session
         self.pub_socket = pub_socket
         self.parent_header = {}
 
     def __call__(self, obj):
         if obj is None:
             return
 
         __builtin__._ = obj
+        sys.stdout.flush()
+        sys.stderr.flush()
         msg = self.session.send(self.pub_socket, u'pyout', {u'data':repr(obj)},
                                parent=self.parent_header, ident=self.topic)
 
     def set_parent(self, parent):
         self.parent_header = extract_header(parent)
 
 
 def _encode_binary(format_dict):
     pngdata = format_dict.get('image/png')
     if pngdata is not None:
         format_dict['image/png'] = encodestring(pngdata).decode('ascii')
     jpegdata = format_dict.get('image/jpeg')
     if jpegdata is not None:
         format_dict['image/jpeg'] = encodestring(jpegdata).decode('ascii')
 
 
 class ZMQShellDisplayHook(DisplayHook):
     """A displayhook subclass that publishes data using ZeroMQ. This is intended
     to work with an InteractiveShell instance. It sends a dict of different
     representations of the object."""
 
     session = Instance(Session)
     pub_socket = Instance('zmq.Socket')
     parent_header = Dict({})
 
     def set_parent(self, parent):
         """Set the parent for outbound messages."""
         self.parent_header = extract_header(parent)
 
     def start_displayhook(self):
         self.msg = self.session.msg(u'pyout', {}, parent=self.parent_header)
 
     def write_output_prompt(self):
         """Write the output prompt."""
         if self.do_full_cache:
             self.msg['content']['execution_count'] = self.prompt_count
 
     def write_format_data(self, format_dict):
         _encode_binary(format_dict)
         self.msg['content']['data'] = format_dict
 
     def finish_displayhook(self):
         """Finish up all displayhook activities."""
+        sys.stdout.flush()
+        sys.stderr.flush()
         self.session.send(self.pub_socket, self.msg)
         self.msg = None