add flushing of stdout to update on key event

Doing this as a demo for UC Berkeley Practical Neuroimaging class on
contributing to open source while getting your work done

Author: ivanov

examples/event_handling/keypress_demo.py

@@ -4,12 +4,14 @@
 Show how to connect to keypress events
 """
 from __future__ import print_function
+import sys
 import numpy as np
 import matplotlib.pyplot as plt
 
 
 def press(event):
     print('press', event.key)
+    sys.stdout.flush()
     if event.key=='x':
         visible = xl.get_visible()
         xl.set_visible(not visible)