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To: python-list@python.org
From: Dennis Lee Bieber <wlfraed@ix.netcom.com>
Subject: Re: Implicit conversion to boolean in if and while statements
Date: Mon, 16 Jul 2012 13:28:14 -0400
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Xref: csiph.com comp.lang.python:25431

On 16 Jul 2012 02:38:35 GMT, Steven D'Aprano
<steve+comp.lang.python@pearwood.info> declaimed the following in
gmane.comp.python.general:

> On Sun, 15 Jul 2012 12:02:37 -0500, Andrew Berg wrote:
> 

> > Okay, I see the value in this, but I don't understand why None has a
> > truth value.
> 
> And this is exactly the sort of mental confusion that Laura Crichton 
> warned about (see the link I included earlier).
>

	Would one rather have the behavior seen in SQL for Null?
http://www.firebirdsql.org/file/documentation/reference_manuals/user_manuals/Firebird-Null-Guide.pdf

	Hey, let's turn the IF statement into tri-state logic...

	if cond:
		#true branch
	else:
		#false branch
	unknown:
		#when cond includes a None term that was NOT explicitly
		#part of a "... is {not} None" clause
-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
        wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/