On 2013年9月13日 22:31:02 +0300 Serhiy Storchaka <[email protected]> wrote: > 13.09.13 21:40, Antoine Pitrou написав(ла): > > Both are instances of a more general pattern, where a given > > transformation function is applied to keys when looking them up: that > > function being ``str.lower`` in the former example and the built-in > > ``id`` function in the latter. > > Please use str.casefold in examples. > > > >>> d = TransformDict(str.lower, [('Foo': 1)], Bar=2) > > {'Foo': 1} or [('Foo', 1)].
Ok, thanks. > > Providing a specialized container, not generic > > ---------------------------------------------- > > > > It was asked why we would provide the generic TransformDict construct > > rather than a specialized case-insensitive dict variant. The answer > > is that it's nearly as cheap (code-wise and performance-wise) to provide > > the generic construct, and it can fill more use cases. > > Except lightweight IdentityDict which can be implemented more efficient > than TransformDict(id). It doesn't need in calling the transform > function, computing the hash of transformed key, comparing keys. > But > perhaps in many cases TransformDict(id) is enough. That's true. But it's only important if TransformDict is the bottleneck. I doubt the memoizing dictionary is a bottleneck in e.g. the pure Python implementation of pickle or json. > > Python's own pickle module uses identity lookups for object > > memoization: > > http://hg.python.org/cpython/file/0e70bf1f32a3/Lib/pickle.py#l234 > > Also copy, json, cProfile, doctest and _threading_local. Thanks, will add them. Regards Antoine. _______________________________________________ Python-Dev mailing list [email protected] https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com