problem with raw_input and event handlers

Hi all...I am connecting an event handler that collects user input via raw_input. When using GTKAgg as my backend, this works but requires the user to first hit 'enter' before the raw_input prompt is displayed--this extra step of hitting enter is quite cumbersome! When I use the TKAgg backend, I get this error message:
Exception in Tkinter callback
Traceback (most recent call last):
   File "/local/lib/python2.5/lib-tk/Tkinter.py", line 1403, in __call__
     return self.func(*args)
   File "/local/lib/python2.5/site-packages/matplotlib/backends/backend_tkagg.py", line 208, in button_press_event
     FigureCanvasBase.button_press_event(self, x, y, num, guiEvent=event)
   File "/local/lib/python2.5/site-packages/matplotlib/backend_bases.py", line 911, in button_press_event
     func(mouseevent)
   File "tktest.py", line 15, in printpoint
     color = str(raw_input("Enter color: "))
RuntimeError: can't re-enter readline

I am using Tcl/Tk 8.4.14, python2.5, and matplotlib0.90. The test code I'm using follows.

Thanks for any help!
Matt

···

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import pylab,scipy

def printpoint(event):
      color = str(raw_input("Enter color: "))
      text = "%d , %d" % (event.xdata,event.ydata)
      pylab.text(event.xdata,event.ydata,text,color=color)

data = scipy.arange(100.)
pylab.plot(data)
pylab.connect('button_press_event',printpoint)