Moving a window on the screen

[ast]

Hi

Why the following program doesn't work ?

for x in range(0, 100, 10):
    fen.geometry("200x200+%d+10"   %   x)
    time.sleep(0.5)


where fen is a window (fen = Tk())

The fen window goes from it's initial location to the last one
but we dont see all the intermediate steps


thx