flush messages printed during startup

Prevents print statements during init methods from being associated with the first execution.

closes  #1022

IPython/lib/pylabtools.py

@@ -19,6 +19,7 b' Authors'
 # Imports
 #-----------------------------------------------------------------------------
 
+import sys
 from io import BytesIO
 
 from IPython.utils.decorators import flag_calls
@@ -317,6 +318,8 b' def pylab_activate(user_ns, gui=None, import_all=True, shell=None):'
     print """
 Welcome to pylab, a matplotlib-based Python environment [backend: %s].
 For more information, type 'help(pylab)'.""" % backend
+    # flush stdout, just to be safe
+    sys.stdout.flush()
     
     return gui
 

IPython/zmq/kernelapp.py

@@ -287,6 +287,10 b' class KernelApp(BaseIPythonApplication):'
         self.write_connection_file()
         self.init_io()
         self.init_kernel()
+        # flush stdout/stderr, so that anything written to these streams during
+        # initialization do not get associated with the first execution request
+        sys.stdout.flush()
+        sys.stderr.flush()
 
     def start(self):
         self.heartbeat.start()