[Zope] Boolean properties ( Zope 2.5)

[Chris Beaven]

I agre that in the 'a' and 'b' case it's not so much a question of logic as
it is value representation. I included it in the discussion because I
thought it was interesting.

Also, the page I linked to had a definition of Python's true / false:
0, '', [], (), {}, and None are false in a boolean context; everything else
is true

PS. I have actually used the 'and-or trick' once or twice after I found out
about this
-----Original Message-----
From: Eron Lloyd [mailto:elloyd@lancaster.lib.pa.us]
Sent: Thursday, 5 September 2002 10:55 a.m.
To: Chris Beaven
Cc: Brian Sullivan; zope@zope.org
Subject: RE: [Zope] Boolean properties ( Zope 2.5)


Correct, but that's only when doing a comparison. Python will perform a
lazy comparison, returning either the first true value (in an "or"
expr.), or the last true value in an "and" expr. In the case stated,
it's not so much a question of logic as it is value representation.
Honestly, I don't understand why you would ever want the actual *value*
returned by a boolean expression, instead of it's state. What needs to
be done probably is a re-examination of the problem at hand.

Cheers,

Eron

On Wed, 2002-09-04 at 18:29, Chris Beaven wrote:
> In Python, 'and' and 'or' perform boolean logic as you would expect, but
> they do not return boolean values; they return one of the actual values
they
> are comparing. 
> 
> >>> 'a' and 'b'
> 'b'
> >>> '' and 'b'
> ''
> 
> >>> 'a' or 'b'
> 'a'
> >>> '' or 'b'
> 'b'
> 
> http://diveintopython.org/apihelper_andor.html
> 
> Well, I found it interesting...
> 
> 
> -----Original Message-----
> From: Brian Sullivan [mailto:brians@meetingbywire.com]
> Sent: Thursday, 5 September 2002 2:27 a.m.
> To: zope@zope.org
> Subject: [Zope] Boolean properties ( Zope 2.5)
> 
> 
> I a trying to figure out what values are stored in Boolean typed
> properties of a Zope object in order to display information in and
> retrieve and set information from form checkboxes.
> 
> What values are actually set/returned in boolean properties?
> 
> 
> _______________________________________________
> Zope maillist  -  Zope@zope.org
> http://lists.zope.org/mailman/listinfo/zope
> **   No cross posts or HTML encoding!  **
> (Related lists - 
>  http://lists.zope.org/mailman/listinfo/zope-announce
>  http://lists.zope.org/mailman/listinfo/zope-dev )
> 
> _______________________________________________
> Zope maillist  -  Zope@zope.org
> http://lists.zope.org/mailman/listinfo/zope
> **   No cross posts or HTML encoding!  **
> (Related lists - 
>  http://lists.zope.org/mailman/listinfo/zope-announce
>  http://lists.zope.org/mailman/listinfo/zope-dev )
> ---
> [This E-mail scanned for viruses by Declude Virus]
> 
> 


---
[This E-mail scanned for viruses by Declude Virus]