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Date: Thu, 02 Jan 2014 20:16:51 -0800
From: Ethan Furman <ethan@stoneleaf.us>
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Xref: csiph.com comp.lang.python:63034

On 01/02/2014 04:06 PM, Chris Angelico wrote:
>
> Here's a crazy idea. Suppose we have a "sticky falseness" that can
> quietly propagate through an expression the way a NaN can... then we
> could just float that right through the .group() call.
>
> class truth:
>      def __new__(cls, x):
>          if x: return x
>          return object.__new__(cls)
>      def __bool__(self):
>          return False
>      def __getattr__(self, name):
>          return self
>      def __call__(self, *args, **kwargs):
>          return self
>      def __repr__(self):
>          return repr(False)
>
> Pass any object through truth() and it'll either stay the same (if
> it's true) or become this object (if it's false). You can then carry
> on with other method calls, and they'll all happily return false.

An interesting idea.  You'd need to add (at least) __getitem__, and I'll 
probably call it `maybe`, myself.  ;)


> (I'm not sure if I'm using __new__ correctly; I've never actually done
> it in production code, and the info I found online was mainly Py2
> examples. Should that be done with super(), or is that applicable only
> once there's an actual instance with a real MRO?)

I haven't tested it, but your __new__ looks fine.  The only thing you 
lose by not calling super() is the inability for cooperative multiple 
inheritance, except as the ultimate base class.

--
~Ethan~