I feel that Python lacks one useful data structure: an ordered dictionary. I find such data structures v. useful in C++. I know that in Python the sort function is v. fast, but often I prefer never to sort but simply to use an ordered data structure in the first place. (I'm aware that for ordered lists I can use the bisect module, but I want an ordered key-value data structure.)
I think other people must find such things useful. There are three implementations on the Python Cookbook site, and one on PyPI, all in pure Python (plus I have my own implementation, also pure Python). I would suppose that it would be better if it was implemented in C--- for example, my own pure Python ordered dict loads data about eight times slower than the built-in dict. Nonetheless, I still find it worth using for the convenience it offers. Do other Python programmers feel this lack? Is this worth a PEP? [I originally asked about this on the P3K mailing list, but then realised that it isn't version-specific really.] -- http://mail.python.org/mailman/listinfo/python-list
