The zc.lockfile package provides a basic portable implementation of
interprocess locks using lock files. The purpose if not specifically
to lock files, but to simply provide locks with an implementation
based on file-locking primitives. Of course, these locks could be
used to mediate access to other files. For example, the ZODB file
storage implementation uses file locks to mediate access to
file-storage database files. The database files and lock file files
are separate files.

WWW:  http://pypi.python.org/pypi/zc.lockfile