python定义一个类实例作为ftp回调方法，python回调,class Writer

python定义一个类实例作为ftp回调方法，python回调,class Writer

class Writer:    def __init__(self, file):        self.f = open(file, "w")    def __call__(self, data):        self.f.write(data)        self.f.write('\n')        print dataFILENAME = "AutoIndent.py"writer = Writer(FILENAME)import ftplibftp = ftplib.FTP('127.0.0.1', 'book', 'bookpw')ftp.retrlines("RETR %s" % FILENAME, writer)