Is this what pandas MultiIndex does (in Cython)? * http://pandas.pydata.org/pandas-docs/dev/api.html#reshaping-sorting * http://toolz.readthedocs.org/en/latest/api.html On Mon, Dec 1, 2014 at 8:24 AM, David Wilson <dw+python-ideas@hmmz.org> wrote:
On Mon, Dec 01, 2014 at 01:13:41PM +0100, SF Markus Elfring wrote:
Hello,
I find a data structure like it is provided by the "Boost Multi-index Containers Library" interesting for efficient data processing. http://www.boost.org/doc/libs/1_57_0/libs/multi_index/doc/index.html
This came up on #python just last week, and I've personally encountered a desire for something similar a bunch of times. Probably, though, the ideal interface to something like this would need some time to evolve before it would be useful to include in the stdlib, along with some motivating use cases -- at least, it would be nice if there were one or two third party implementations to compare before settling on an interface. I can't think of any existing implementations that operate on purely in-memory structures.
Boost::multiindex is pretty awesome, but its interface is also somewhat complicated, and a 1:1 translation wouldn't make for a pretty Python experience.
I thought about this a little bit last week, initially starting with a "MultiSet" type interface, where the "default" interface for the container emulated a regular set object. But that would prevent having sets of things unless they were hashable (instead of, say, merely having properties that were orderable). In applications where I'd like to use a structure like this, often the element type is mutable.
My second idea was for something like an "IndexedList" type, where the default interface mimicked the built-in list. This would allow generic use of the container with code that wasn't expecting it, and avoid the hashability issue from before.
Perhaps something like:
lst = IndexedList() lst.add_unique_index('id', lambda o: o['id']) lst.add_index('age', lambda o: o['age'])
lst.append({'id': 1, 'age': 50}) lst.append({'id': 1, 'age': 50}) # KeyError
lst.append({'id': 2, 'age': 51})
assert lst.indices['id'][1]['age'] == 50
slice = lst.indices['age'][40:50] # No idea what would be returned here, some kind of view perhaps. assert len(slice) == 2
Following on from the blist thread a few months back, this is another example of a container that would be easy to construct if Python had some kind of built-in ordered mapping type.
David
How are the chances to integrate a class library with similar
functionality into the Python software infrastructure?
https://bugs.python.org/issue22957
Regards, Markus _______________________________________________ Python-ideas mailing list Python-ideas@python.org https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct: http://python.org/psf/codeofconduct/
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