gistfile1.py

class MathOpThree(object):
    
    def sum(self, node):
        if len(node.childrens) == 2:
            print node.getTokenValue()
            #node.setTokenValue(self.sum(node.childrens[0]).getTokenValue() + self.sum(node.childrens[1]).getTokenValue())
            node.setTokenValue(self.doMathOperation(node.getTokenType(), self.sum(node.childrens[0]).getTokenValue(), self.sum(node.childrens[1]).getTokenValue()))
        return node    
    
    def doMathOperation(self, mathOpString, tokenValue1, tokenValue2):
        
        dicti = {"PLUS" : tokenValue1+tokenValue2,
                 "MINUS" : tokenValue1-tokenValue2,
                 "TIMES" : tokenValue1*tokenValue2,
                 "DIVIDE" : tokenValue1/tokenValue2}
        
        return dicti[mathOpString]