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Date: Fri, 24 Feb 2012 10:39:26 +1100
Subject: Re: sum() requires number, not simply __add__
From: Chris Angelico <rosuav@gmail.com>
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On Fri, Feb 24, 2012 at 10:33 AM, Steven D'Aprano
<steve+comp.lang.python@pearwood.info> wrote:
> Yes, deleting _sentinel will cause the custom sum to fail, and yes, you
> have missed something.
>
> If the caller wants to mess with your library and break it, they have
> many, many ways to do so apart from deleting your private variables.

I was looking at the module breaking itself, though, not even waiting
for the caller to do it.

ChrisA