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From: Ian Kelly <ian.g.kelly@gmail.com>
Date: Mon, 29 Jul 2013 11:19:22 -0600
Subject: Re: collections.Counter surprisingly slow
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On Mon, Jul 29, 2013 at 5:49 AM, Joshua Landau <joshua@landau.ws> wrote:
> Also, couldn't Counter just extend from defaultdict?

It could, but I expect the C helper function in 3.4 will be faster
since it doesn't even need to call __missing__ in the first place.
And the cost (both in terms of maintenance and run-time) of adding
defaultdict to the Counter MRO just to reuse one tiny __missing__
method seems questionable, especially after taking into account that
the constructor signature is incompatible.