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From: Chris Angelico <rosuav@gmail.com>
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Subject: Re: Operator Precedence/Boolean Logic
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On Thu, Jun 23, 2016 at 10:37 PM, Steven D'Aprano <steve@pearwood.info> wrote:
> I acknowledge, cheerfully, that there might be a mismatch between what you
> expect and what the object actually does. "I expect empty containers to be
> falsey, and non-empty ones to be truthy; but this RedBlackTree object is
> always false even if it has many items; and this SortedDict is always true
> even when it is empty."
>
> That's a nuisance and a pain when it happens, but it's arguably a bug in the
> object or at least a misfeature...

As evidenced by the change to time truthiness, yes, that's the
object's fault. If your RedBlackTree object were always *true*, I'd
call it a missing feature ("please add a __bool__ that distinguishes
empty trees from trees with content"), but always *false* would be a
bug. A SortedDict implies by its name that it should be extremely
dict-like, so that would be a strong argument for its truthiness to
follow a dict's. Either way, the misbehaviour gets pointed back at the
object in question.

ChrisA