How call method from a method in same class?

[Dave]

As classes get more complex, it is good to call a function to do some of 
the processing, and make the code easier to follow.  My question is how 
to do that?  I've attached some silly code to illustrate the point.  The 
error is: name 'validScale' is not defined.  Well, yes it is, but maybe 
not the correct way.  Suggestions?

Dave,

class TempConverter():
     """ Temperature Converter converts a tempeature from one scale
         to another scale.  For example: 32, F, C will return
         0 degrees C
     """

     def __init__(self, temperature, scale, newScale):
         self.temperature = temperature
         self.scale = scale
         self.newScale = newScale

     def validScale(self, scaleName):
         if scaleName.upper == 'F' or 'C' or 'K':
             return True
         else:
             return False

     def convertTemp(self):
         """ Converts temperature scale if scales valid."""
         if validScale(self.scale):
             scaleValid = True
         if validScale(self.newScale):
             newScaleValid = True
         if scaleValid and newScaleValid:
             print('Scale converted')
         else:
             msg = "There was and error with the scales entered.\n"
             msg = msg + "You entered: " + self.scale
             msg = msg + ' ' 'and' + self.newScale
             print(msg)

if __name__ == "__main__":
     myclass = TempConverter(32, 'f', 'c')
     myclass.convertTemp()