Threads, GIL and re.match() performance

[Jeff]

> 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.