> However, I assumed that calls to (thread safe) C Library functions > release the global interpreter lock.
This is mainly applicable to external C libraries. The interface to them may not be thread-safe; anything that uses the Python API to create/manage Python objects will require use of the GIL. So the actual regex search may release the GIL, but the storing of results (and possibly intermediate results) would not. -- http://mail.python.org/mailman/listinfo/python-list
