Steve Holden schrieb: > Perhaps now the answer top your question is more obvious: there is by no > means universal agreement on what an "ordered dictionary" should do. > Given the ease with which Python allows you to implement your chosen > functionality it would be presumptuous of the core developers to favour > any one of the several reasonable alternatives that might be chosen.
The discussion showed indeed that there are some points which are not so straightforward as I believed. But I still don't see the "several reasonable alternatives". So far all implementations I have seen are basically pretty similar. Is there any implementation that is basically different from Foord/Larosa's odict? I still don't see a principal problem here, just the problem that the existing implementations are not well enough thought-out and sophisticated enough. > Given the ease with which Python allows you to implement your chosen > functionality it would be presumptuous of the core developers to > favour any one of the several reasonable alternatives that might be > chosen. You could say the same about the idea of sets in Python, and it is probably the reason why it took so much time until they became a part of Python. I wished that had happened earlier, since sets are "the" basic mathematic structure. I'm now very happy to have sets not only in the standard lib but even as built-in types and I'm sure there hasn't been "universal agreement" on how sets should be implemented either. I don't think it was presumptuous to finally settle down on one implementation. Of course, ordered dictionaries are no candidates for becoming built-in data types, and the existing implementations are not sophisticated and mature enough to go to the standard lib right now. But principally, if an improved version is developed (maybe on the occasion of this thread) and will be tested and proven, why should it not go to the standard lib some day? BTW, somebody has suggested it could go to "collections" which sounds like the right place, but the description says the module is intended for "High-performance container datatypes", and, as has been discussed, ordered dictionaries are not used for performance or efficiency reasons, but rather for reasons of convenience. So *if* they ever go to the standard lib, I'm not sure whether "collections" would be the right place. Or collections will need a different description - maybe there are other interesting basic collection types which are chosen for convenience, not for performance (for instance, ordered sets)? -- Christoph -- http://mail.python.org/mailman/listinfo/python-list
