expiringdict is a Python caching library.  The core of the library is
ExpiringDict class which is an ordered dictionary with auto-expiring values for
caching purposes.  Expiration happens on any access, object is locked during
cleanup from expired values.  ExpiringDict can not store more than max_len
elements - the oldest will be deleted.

WWW: https://github.com/mailgun/expiringdict