calling a class method from a menu in a different class

[Chris Hare]

What I am trying to do is call a class function from a menu, for example

		displaySubMenu.add_radiobutton(label="Medium", 
		variable=radarPanelSize, command=radarWidgets.refresh) 

class radarWidgets:
	def __init__(self,root):
		self.window = root
	def refresh(self):
		global radar
		global refreshTimer
		self.refreshTimer.cancel()
		logging.debug("handlesRadarRefreshByTimer()")
		#
		# destroy the existing frame the radar is in
		#
		self.w.destroy()
		self.lblLastUpdate.destroy()
		self.btnRefresh.destroy()
		#
		# rebuild the radarWidgets
		#
		self.createImage()
		self.refreshTimer = threading.Timer( 900, self.refresh)
		self.refreshTimer.start()

This doesn't work because the instance of radarWidgets was defined in a different class ......

class mainDisplay:
	def __init__(self,root):
		self.window = root
	def show(self):		
		#
		# Configure the base frame
		# 
		base=Frame(self.window,bg=backColor,width=1200, height=800)
		base.grid()
		frameRadar = Frame(base, bd=0, bg=backColor)
		frameRadar.grid(row=2,column=1,sticky=N+E+S+W)
		#
		radar = radarWidgets(frameRadar)
		radar.show()

so the actual instance is called "radar".  If I put the instance name in the menu item, I get an error that "radar" is unknown.  If I use RadarWidgets.refresh ins the command for the menu, I get the error:

TypeError: unbound method refresh() must be called with radarWidgets instance as first argument (got nothing instead)

Any ideas?

Thanks!