Hi, Now that issue 13703 has been largely settled, I want to propose my new dictionary implementation again. It is a little more polished than before. https://bitbucket.org/markshannon/hotpy_new_dict Object-oriented benchmarks use considerably less memory and are sometimes faster (by a small amount). (I've only benchmarked on my old 32bit machine) E.g 2to3 No speed change -28% memory GCbench +10% speed -47% memory Other benchmarks show little or no change in behaviour, mainly minor memory savings. If an application is OO and uses lots of memory the new dict will save a lot of memory and maybe boost performance. Other applications will be largely unaffected. It passes all the tests. (I had to change a couple that relied on dict repr() ordering) Cheers, Mark.