def createTask(self):
        """ generates a new task which can be passed through the eval function """
        if self.trainingParameter.operation in ['*', '+', '-']:
            numbers = str([self.createNumber(digits) for digits in self.trainingParameter.digitsPerNumber])
            return numbers.replace(", " , " %c " % self.trainingParameter.operation)[1:-1]

        elif self.trainingParameter.operation == '/':
            key = tuple(self.trainingParameter.digitsPerNumber)
            if key in DivisionCache.divisions:
                divisions = DivisionCache.divisions[key]
                numbers   = str(divisions[random.randrange(0, len(divisions)-1)])
                return numbers.replace(", " , " %c " % self.trainingParameter.operation)[1:-1]
        # not supported
        return ""
 generates a new task which can be passed through the eval function 
recipes/Python/578111_Learning_calculate_mental/recipe-578111.py