[Zope] A quick zope/python question

[Jonathan]

Thanks to everyone for setting me straight!

I have been (erroneously!) assuming that any defined object would evaluate 
to 'true'.

Thanks again.

Jonathan

----- Original Message ----- 
From: "Jens Vagelpohl" <jens at dataflake.org>
To: "[Zope] Mailing List" <zope at zope.org>
Sent: Tuesday, May 09, 2006 11:25 AM
Subject: Re: [Zope] A quick zope/python question


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> On 9 May 2006, at 16:18, Jonathan wrote:
>> gc= <TransientObjectContainer at GarbageCollector>
>> GarbageCollector exists
>>
>>
>> I think I am misunderstanding something basic about python/zope  here. 
>> Why does a TOC object evaluate to false?
>
> I think the basic misunderstanding is about what happens if you say...
>
> if FOO: ...
>
> Python will try to evaluate using steps such as looking for methods  like 
> __nonzero__, __len__, etc, and you're not aware what these may  evaluate 
> to given your object. A Folder, for example, evaluates to  False when it 
> is empty.
>
> You should use a different test to determine if that item exists.
>
> jens
>
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