从基类扩展方法时的TypeError

Question

我试图测试一个简单的Python继承案例,但我在理解Python解释器吐出的错误时遇到了问题.

class Mainclass(object):
    """
     Class to test the inheritance
    """
    def __init__(self,somevalue):
        self.somevalue = somevalue
    def display(self):
        print(self.somevalue)


class Inherited(Mainclass):
    """
    Inherited class from the Main Class
    """
    def display(self):
        print("**********")
        Mainclass.display()
        print("**********")

c = Inherited(100)
c.display()

我只是试图在Inherited类中显示的输出中添加星号,那么为什么它会因以下错误而失败？

Traceback (most recent call last):
line 21, in <module>
c.display()
line 17, in display
Mainclass.display()
TypeError: display() missing 1 required positional argument: 'self'

Answer 1

调用它时,需要将self从继承类的display方法传递给Mainclass.display()方法.所以你的代码变成:

class Mainclass(object):
  """
   Class to test the inheritance
  """
  def __init__(self,somevalue):
      self.somevalue = somevalue
  def display(self):
      print(self.somevalue)


class Inherited(Mainclass):
  """
  Inherited class from the Main Class
  """
  def display(self):
      print("**********")
      Mainclass.display(self)
      print("**********")

c = Inherited(100)
c.display()

希望这可以帮助!:)