Change Directory on a per Thread Basis

Hi guys, im currrently writing a small ftp server in python in which a client connects to the server and can transfer files, list the directory and change directory on the server. this is a multi threaded server and this causes me problems when changing directories because the directory seems to be kept on a process basis and not a per thread basis. This would mean that if two clients were connected and one changed the directory the change would apply to both clients. I would like my code to be able to change directory for a particular thread only. Ive looked all over for a solution. Any ideas?