使用Python检查远程SSH服务器上的文件是否存在

I have two servers A and B. I'm suppose to send, let said an image file, from server A to another server B. But before server A could send the file over I would like to check if a similar file exist in server B. I try using os.path.exists() and it does not work.I have two servers A and B. I'm suppose to send