> First minimal test case: > > class Leaker(object): > def __hash__(self): return 1 > > for i in range(10): > hash( Leaker() ) > print '*' * 10, 'total refs:', sys.gettotalrefcount() This one is clearly a missing decref in slot_tp_hash(), leaking a reference to the integer result object. If SourceForge wakes up, I've got a fix ready to check in.