[Python-Dev] counterintuitive behavior (bug?) in Counter with +=

[Raymond Hettinger]

On Oct 3, 2011, at 6:12 AM, Lars Buitinck wrote:

>  After some digging, I found out that Counter [2] does not
> have __iadd__ and += copies the entire left-hand side in __add__!

This seems like a reasonable change for Py3.3.


> I also figured out that I should use the update method instead, which
> I will, but I still find that uglier than +=. I would submit a patch
> to implement __iadd__, but I first want to know if that's considered
> the right behavior, since it changes the semantics of +=:

Yes, update() is the fastest way.


Raymond

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