python - Matplotlib on click get node -

i want change color on node clicked on

def button_press_callback(event):    print event.x

this event add figure:

    wm.canvas.mpl_connect('button_press_event', button_press_callback)

i want detect on node clicked , change color of node.

when try ind property event object, exception thrown:

 ind = event.ind[0]  attributeerror: mouseevent instance has no attribute 'ind'

but in examples see other users can ind property.

Brande