[Zope] Re: TAL: test() or condition Howto?

[Paul Winkler]

On Fri, Jan 31, 2003 at 10:12:14AM -0600, Evan Simpson wrote:


> Thanks to the way Python's "and" works, you can do the following:
> 
> <td tal:define="x python:myImportantCondition and myExpensiveMethod()"
>     tal:content="python:x or default">myDefaultString</td>

Yes, i use this idiom a lot, abbreviated to:

<td tal:content="python:myImportantCondition and myExpensiveMethod() or default">
my default string
</td>

However, be wary of this: the inevitable need to add "just one more option" 
can lead to some REALLY ugly expressions. You don't want to end up with expressions like:

<span tal:content="python:here.foo(bar) and here.that and not (request.the_other) or not container.spam or here.get_some_food(request.food_type or 'bacon')">
  what on earth is going to end up here?
</span>

as a rule of thumb, I like to refactor anything that uses more than 2 of "and" or "or".

-- 

Paul Winkler
http://www.slinkp.com
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