Ftp读取文件到BytesIO缓存读文件

def openFtpFileBytesIO(fileName,ftpServer,ftpUser='anonymous',ftpPass='',port=21):
    """
    读ftp文件到缓存
    """
    ftps = FTP()
    ftps.connect(ftpServer,port)
    ftps.login(ftpUser,ftpPass)
    download_file = BytesIO()
    ftps.retrbinary('RETR ' + str(fileName), download_file.write)
    download_file.seek(0)
    return download_file

def readFile(f):
    while True:
        line = f.readline()
        if line:
            print(line)
        else: 
            f.close()
            break

if __name__=="__main__":
    f=openFtpFileBytesIO('test.csv','192.168.0.3')
    readFile(f)