(Google -- which normally does an absolutely stunning job of directing me to answers to Zope questions -- has drawn a blank on this one:) I have an external method that writes stuff to a file. I want to synchronize access to the file so that multiple callers can be adding stuff to the file without problems. Without any synchronization I get interleaved output most of the time and occasionally an error message like this: "Z2 CONFLICT Competing writes at, /foo" I tried using the threading module and creating a Lock object as a global in the external method. This does not help as each request gets allocated its own Lock object. I tried Rlock got an error message I didn't understand and concluded I don't know what I'm doing:-) Any pointers to the best way to do synchronization of access to the filesystem from external methods? regards, Sean McGrath