title: Cannot print out "event.char" using Tkinter
body: <p>I run this successfully in Python 2.7 with Pycharm IDE in one Macbook. I press arrow up key, event.char is not null, it can print out something. However, in the other Macbook or windows system, when I press keys which are not letters, it can not print out anything, all I see is "press: ". When I press letter key,it worked fine, and it print out the letters such like "press : A". Any thought is appreciated.</p>
  
  <pre><code>     #
  from Tkinter import *
  #Entry
  def printkey(event):
      print('press:' + event.char)
  #
  root = Tk()
  #input
  entry = Entry(root)
  #
  entry.bind('&lt;Key&gt;', printkey)
  #
  entry.pack()
  root.mainloop()
  </code></pre>