creating a variable in a method and using in another method

[ridgerunnersjw]

Good evening......
Can someone please tell me the correct way to create a variable within a method and then be able to re-use that variable internal to the class within another method? As an example I tried this below with __usb and __SG....in particular __SG gets defined in open method and I want to re-use it in close method...Thank you for all responses

	def open(self):
		k = visa.ResourceManager()
		try:
			__usb = k.list_resources()[1]
		except IndexError:
			print ('Make sure equipment is turned on')			
		try:
			__SG = k.open_resource(__usb)
		except:
			print ('USB Resource could not be opened')
		else:		
			print ('Success opening USB resource')
		
	def close(self):
		__SG.close()
		print ('Success closing resource')