class Processor(object):
    def __init__(self, reader, writer):
        self.reader = reader
        self.writer = writer
    def process(self):
        while 1:
            data = self.reader.readline(  )
            if not data: break
            data = self.converter(data)
            self.writer.write(data)
    def converter(self, data):
        assert 0, 'converter must be defined'