python - 一个类如何从另一个类继承？

Question

一个类如何继承另一个类？我正在尝试通过以下示例来实现它:

class parents(object):
      def __init__(self,dim_x, dim_y, nameprefix, sequence_number):
          if not isinstance(dim_x, (int, float, long)):
             raise TypeError("Dimension in x must be a number")
          else:
             self.sizex=str(int(dim_x))
          if not isinstance(dim_y, (int, float, long)):
             raise TypeError("Dimension in y must be a number")
          else:
             self.sizey=str(int(dim_y))
          if not isinstance(nameprefix, string_types):
              raise TypeError("The name prefix must be a string")
          else:
              self.prefix=nameprefix
          if not isinstance(sequence_number, (int, float, long)):
             raise TypeError("The sequence number must be given as a number")
          else:
             self.sqNr=str(int(sequence_number))

我希望 child 类从 parents 类继承 prefix 和 sqNr

class child(parents):
      def __init__(self,image_path='/vol/'):
         self.IMG_PATH=image_path
         self.ref_image=self.prefix+'_R_'+self.sqNr
         logger.debug('Reference image: %s', self.ref_image)

并使用以下行运行它，但我收到一条错误消息:

>>> p=parents(300, 300, 'Test',0 )
>>> p.prefix
'Test'
>>> c=child(p)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 4, in __init__
AttributeError: 'child' object has no attribute 'prefix'

我不明白我的实现有什么问题，有什么建议吗？

Answer 1

child 需要为 parents 获取所有参数，并将它们一起传递。您通常不会将父类(super class)实例传递给子类；那是组合，而不是继承。

class child(parents):
    def __init__(self, dim_x, dim_y, nameprefix, 
                 sequence_number, image_path='/vol/'):
        super(child, self).__init__(dim_x, dim_y, nameprefix, 
                                    sequence_number)
        self.IMG_PATH = image_path
        ...

这被称为:

c = child(300, 300, 'Test', 0)

您不需要创建parents 实例，直接创建child。

请注意，根据 style guide ，类名实际上应该是 Parent 和 Child。