Sean McGrath writes:

I want to synchronize ...

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....

As you observed, each thread gets its own global namespace for a file containing an external method. The namespace of a true Python module, however, is shared by all threads. Therefore, it is a good place for your lock. Do the following (or something along similar lines): * create a properly named subpackage in "lib/python/Shared" (to avoid name clashes), say "myCompany". * create a Python module in "myCompany", say "myLock.py". * create your lock in this module, say "Lock" * access it in your external method by: from Shared.myCompany.myLock import Lock Dieter