Checking a file existence on a remote SSH server using Python

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.

print os.path.exists('ubuntu@serverB.com:b.jpeg')

The result return a false even I have put an exact file on server B. I'm not sure whether is it my syntax error or is there any better solution to this problem. Thank you