python - 根据传递给构造函数的参数实现Python类

Question

我正在实现一个Python类，它在构造函数中构造另一个对象，其类型是根据传递给它的参数确定的。例如，在下面的代码中，“workerA”具有类“MyAClass”的行为，而“workerB”对象具有的行为“MyBClass”。

我使用此方法而不是从基类派生不同的类，因为 BaseClass 已在无法更改的不同代码中使用。因此，如果我想要 BaseClass 的另一种行为作为 "MyBClass" 行为，那么我只需要将参数 dbtype = "MyBClass" 传递给它。

是否有更好的方法可以使用并给出相同的结果？

  import sys

  # MyAClass definition
  class MyAClass :

     def __init__(self, serverSettings):
        self._serverSettings = serverSettings

     def initialize(self):
        self._init = 1;
        print("Calling", sys._getframe(1).f_code.co_name)

     def add(self):
        self._init = 2;
        print("Calling", sys._getframe(1).f_code.co_name)

     def finalize(self):
        self._init = 3;
        print("Calling", sys._getframe(1).f_code.co_name)

     def __del__(self):
        print('Calling destructor of class ', self.__class__.__name__)


  # MyBClass definition
  class MyBClass :

     def __init__(self, serverSettings):
        self._serverSettings = serverSettings

     def initialize(self):
        self._init = 1;
        print("Calling", sys._getframe(1).f_code.co_name)

     def add(self):
        self._init = 2;
        print("Calling", sys._getframe(1).f_code.co_name)

     def finalize(self):
        self._init = 3;
        print("Calling", sys._getframe(1).f_code.co_name)

     def __del__(self):
        print('Calling destructor of class ', self.__class__.__name__)


  # The base class which will be called in main program
  class BaseClass :

     def __init__(self, serverSettings, dbtype = None):

        if(dbtype == None):
           self.__worker = MyAClass(serverSettings)
        elif(dbtype == "MyBClass") :
           self.__worker = MyBClass(serverSettings)
        else :
           print("Undefined type")

     def initialize(self):
        self.__worker.initialize()

     def add(self):
        self.__worker.add()

     def finalize(self):
        self.__worker.finalize()


  if __name__ == "__main__":

     serverSettings = dict()

     serverSettings["address"] = "localhost"
     serverSettings["name"] = "Testname"

     workerA = BaseClass(serverSettings)
     workerA.add()

     workerB = BaseClass(serverSettings, dbtype = "MyBClass")
     workerB.finalize()

Answer 1

我知道这不会产生与原始程序相同的输出，但是这样的东西可以满足您的目的吗？除非您查询方法名称(如上面所示)，否则您应该得到功能相同的结果。

class BaseClass :
    def __init__(self, serverSettings, dbtype=None):

        if(dbtype == None):
           self.__worker = MyAClass(serverSettings)
        elif(dbtype == "MyBClass") :
           self.__worker = MyBClass(serverSettings)
        else :
           print("Undefined type")

    def __getattribute__(self, x):
        settings = object.__getattribute__(self, '__dict__').get('_BaseClass__worker')
        return settings.__getattribute__(x)

或者，使用一些像这样的类扭曲:

class BaseClass :
    def __init__(self, serverSettings, dbtype='MyAClass'):
        dbtypes = {'MyAClass': MyAClass,
                    'MyBClass': MyBClass}
        if dbtype not in dbtypes:
           raise("Undefined type")
        self.__class__ = dbtypes[dbtype]
        self.__init__(serverSettings)