defaultdict and ordered defaultdict

[chebee7i]

Could we also get a defaultdict and an ordered defaultdict? The latter would be especially helpful snce the typical recommendation is to subclass: http://stackoverflow.com/questions/6190331/can-i-do-an-ordered-default-dict-in-python

Might require a package rename?

[shoyer]

It does seem like a natural fit to add defaultdict in the same model as OrderedDict and rename the module to "cycollections". A pull request would be greatfully accepted!

I'm not so sure about ordered defaultdict, because that is not actually in the standard lib. But that subclass should still work -- if not, it is a bug.

On Mon, Nov 10, 2014 at 9:14 AM, chebee7i notifications@github.com
wrote:

Could we also get a defaultdict and an ordered defaultdict? The latter would be especially helpful snce the typical recommendation is to subclass: http://stackoverflow.com/questions/6190331/can-i-do-an-ordered-default-dict-in-python

Might require a package rename?

Reply to this email directly or view it on GitHub:
#2

[shoyer]

Actually, defaultdict in the Python standard library is already written in C. So there's no point in doing it in Cython.

[chebee7i]

Right, so I guess only the ordered variant would benefit.

[shoyer]

@chebee7i Looks like github mangled my earlier emailed reply about ordered/default dict:

I'm not so sure about ordered defaultdict, because that is not actually in the standard lib. But that subclass should still work -- if not, it is a bug.

Please do give that subclass a try and let me know if for any reason it does not work.

[chebee7i]

It works nicely. https://gist.github.com/chebee7i/49ebf6af69c329f8ffcb

In the gist, the DefaultOrderedDict derives from cyordereddict.OrderedDict, but the default functionality is still pure Python. Since defaultdict is implemented in C, I'm assuming there was some benefit over a pure Python implementation. So perhaps there might be some benefit to a C/Cython implementation of DefaultOrderedDict. But the gist (which would result in compiled code) is probably good for most purposes.

[shoyer]

If you're really concerned about speed, I would consider is making it an extension type instead of a normal class. I found that made a big difference for the speed of OrderedDict.

[shoyer]

I don't see a cython ordered defaultdict fitting in with this project, because it's not part of the standard library. But if you need it, I encourage you to go ahead and do it in your own project!