multiple clients updating same file in ftp

[muttu2244 at yahoo.com]

hi all

am updating the same file in ftp, through multiple clients, but am
scared that two clients may open the same file at a time, and try
updating, then the data updated by one data will be lost.
So i have to provide some lock mechanism to that file in ftp, so how
can i lock it, if one client opens it for updating, so that till it
gets relased it cannot be updated by other clients.
Could u please suggest me the simple solutions through the python code.

thanks for the help
Yogi