python - 在Python中创建一个抽象类

Question

我正在努力将 EFeatureObjective 设为抽象，我知道我可以实现一个类，然后将 calculate_feature_scores 设为抽象，但我所做的事情 -

class EFeatureObjective(bluepyopt.objectives.Objective):

    """EPhys feature objective"""

    def __init__(self, name, features=None):
        """Constructor
        Args:
            name (str): name of this object
            features (list of eFeatures): features used in the Objective
        """

        super(EFeatureObjective, self).__init__(name)
        self.name = name
        self.features = features

    def calculate_feature_scores(self, responses):
        """Calculate the scores for the individual features"""

        scores = []
        for feature in self.features:
            scores.append(feature.calculate_score(responses))

        return scores


class SingletonObjective(EFeatureObjective):

    """Single EPhys feature"""

    def __init__(self, name, feature):
        """Constructor
        Args:
            name (str): name of this object
            features (EFeature): single eFeature inside this objective
        """

        super(SingletonObjective, self).__init__(name, [feature])

    def calculate_score(self, responses):
        """Objective score"""

        return self.calculate_feature_scores(responses)[0]

    def __str__(self):
        """String representation"""

        return '( %s )' % self.features[0]

• 我使用 ABC = abc.ABCMeta('ABC', (object,), {'__slots__': ()}) 将 EFeatureObjective 作为抽象并有

      def calculate_feature_scores(self, responses):                                   
           pass
  

  喜欢

   import abc                                                                           
  
   ABC = abc.ABCMeta('ABC', (object,), {'__slots__': ()})                               
  
  
   class EFeatureObjective(bluepyopt.objectives.Objective, ABC):                           
  
        """EPhys feature objective"""                                                       
        def __init__(self, name, features=None):                                            
              """Constructor                                                                  
  
              Args:                                                                           
              name (str): name of this object                                             
              features (list of eFeatures): features used in the Objective                
              """                                                                             
  
              super(EFeatureObjective, self).__init__(name)                                   
              self.name = name                                                                
              self.features = features                                                        
  
        @abc.abstractmethod                                                                 
        def calculate_feature_scores(self, responses):    
            pass
  
  
   class SingletonObjective(EFeatureObjective):
         .........
         def calculate_feature_scores(self, responses):                                   
             """Calculate the scores for the individual features"""                       
  
             scores = []                                                                  
             for feature in self.features:                                                
             scores.append(feature.calculate_score(responses))                        
  
             return scores     
  

  然后我在SingletonObjective中实现了这个方法，问题是语法方面这可以实现吗？ SingletonObjective 中不提供这些功能。基本上，EFeatureObjective 作用于(eFeatures 列表)，SingletonObjective 作用于此目标内的单个 eFeature。

• 然后，我在 SingletonObjective 中调用了抽象类 EFeatureObjective 抽象方法 calculate_feature_scores，如下

   def calculate_feature_scores(self, responses):
       super(SingletonObjective, self).calculate_feature_scores(responses)
  

  但是然后

   def calculate_score(self, responses):                                               
           """Objective score"""                                                           
  
           return self.calculate_feature_scores(responses)[0]  
  

  索引会出错。

我在这方面已经安静了一段时间，现在我希望 EFeatureObjective 是抽象的，而不创建一个使用不同 Python 版本的类。感谢任何答案。

Answer 1

如果您想要一个无法实例化但可以子类化的类，那么这里有一种方法:

class BaseClass(object):
  def __new__(cls):
    ''' If this is not a subclass being instanciated, then raise an error '''
    if cls is BaseClass:
      raise TypeError('Cannot instantiate this')
    return object.__new__(cls)

   AbstractMethod1 = None

   def __init_subclass__(cls):
     ''' Anytime subclasses are created, make sure they have the right methods '''
     if cls.AbstractMethod1 is None:
       raise TypeError('All subclasses of `base` must define `AbstractMethod1`')