Python: RPN计算器

Question

我正在尝试通过重用类CalculatorEngine来获得一个RPN计算器，如下所示。但是当我运行它时，它显示了一个属性错误：'RPNCalculator‘对象没有'dataStack’属性。我该如何解决这个问题？(我没有包含Stack类，因为这样会有太多代码。)

     class CalculatorEngine(object):
        def __init__(self):
           self.dataStack = Stack()

        def pushOperand(self, value):
           self.dataStack.push(value)

        def currentOperand(self):
           return self.dataStack.top()

        def performBinary(self, fun):
           right = self.dataStack.pop()
           left = self.dataStack.top()
           self.dataStack.push(fun(left, right))

        def doAddition(self):
           self.performBinary(lambda x, y: x + y)

        def doSubtraction(self):
           self.performBinary(lambda x, y: x - y)

        def doMultiplication(self):
           self.performBinary(lambda x, y: x * y)

        def doDivision(self):
           try:
              self.performBinary(lambda x, y: x / y)
           except ZeroDivisionError:
              print("divide by 0!")
              exit(1)

        def doTextOp(self, op):
           if (op == '+'):
              self.doAddition()
           elif (op == '-'):
              self.doSubtraction()
           elif (op == '*'):
              self.doMultiplication()
           elif (op == '/'): self.doDivision()


     class RPNCalculator(CalculatorEngine):
        def __init__(self):
           super(CalculatorEngine, self).__init__()

        def eval(self, line):
           op = line.split(" ")
           try:
              for item in op:
                 if item in '+-*/':
                    self.doTextOp(item)
                 elif item in '%':
                    self.performBinary(lambda x, y: x % y)
                 else:
                    self.pushOperand(int(item))
              return self.currentOperand()
           except ZeroDivisionError:
              print 'divide by 0!'

Answer 1

​

class X(object):
  def __init__(self, name):
    self._name = name

  def doit(self, bar):
    print("Hello")

class Y(X):
  def __init__(self):
    # super(X, self).__init__()
    X.__init__(self, "DDXX")


i = X("Yuze")
j = Y()

​

或者，您可以使用此代码片段来修复它。