wxpython automate progress bar

[Jimmy]

Hi, I want a progress bar to increase automatically, so I wrote code
like this:
current = 0
		while True:
			if current == 100:
				current = 0
			self._gauge.SetValue(current)
			time.sleep(0.1)
			current = current + 1

I put this in the __init__ section, however, the window will never
show! and there are
error message like this:
** (python:28543): CRITICAL **: clearlooks_style_draw_handle:
assertion `width >= -1' failed

can anyone tell me why this happen?Thanks :)