Python クラス オブジェクトとインスタンス オブジェクトの違い

class Main_class_dll():
      

      def __init__(self):
        dllName = "SessionConnector.dll" 
        dllABSPath = os.path.dirname(os.path.abspath(__file__)) + os.path.sep + dllName
        self.dll = cdll.LoadLibrary(dllABSPath)
        self.session_id=''

      def int_create_(self):
         self.dll.Init.restype = c_bool
         sign = self.dll.Init()

      def Create_Session(self,ip,port):
        self.dll.CreateSession.argtypes=[c_char_p,c_char_p]   #输入参数的格式
        self.dll.CreateSession.restype = c_int;               #输出参数的格式
        self.session_id = self.dll.CreateSession(ip,port);

      def send_recv(self,buf):
        time.sleep(2)
        self.dll.SendSessionMsg.restype = c_bool;
        self.dll.SendSessionMsg.argtypes=[c_int,c_char_p,c_uint]
        ret = self.dll.SendSessionMsg(self.session_id, buf, len(buf) + 1);
        self.dll.RecvSessionMsg.argtypes=[c_int,c_char_p,c_uint,c_int]
        self.dll.RecvSessionMsg.restype = c_bool;
        recv_buf = create_string_buffer(1024);
        ret = self.dll.RecvSessionMsg(self.session_id, recv_buf, 1024, 3000);

        self.dll.DestroySession.restype = c_bool;
        ret = self.dll.DestroySession(self.session_id);

        return recv_buf.value

class test:
    data = 1
    def __init__(self):
        self.property=0

    def test2(self):
        print 'hello'

if __name__=='__main__':
    t = test()
    print test.data
    print t.data
    print test.test2
    print t.test2()
    print test.test2(t)