[ZPT] Added Python code blocks to ZPT

[Chris Withers]

Sorry, but -as-many-as-I'm-allowed.

this is horrible :-(

Chris

Ian Bicking wrote:
> Well, ZPT is pretty slow moving these days, but there's a feature that 
> I'd be interested in.  It's inspired by Kid 
> (http://lesscode.org/projects/kid/), which is very similar to ZPT.  In 
> it, you can have Python code:
> 
> <?python
>   ...
> ?>
> 
> But unlike PHP, ASP, and family, the Python code can't produce output 
> and must be self-contained.  This allows for a nice continuum as code 
> becomes more complex; you can start out with a normal tal expression, 
> move to a python: tal expression, and then move things into a header, 
> and finally move things out into an external script.
> 
> For example, imagine a select box:
> 
> <select name="state">
>  <option tal:repeat="state options/states"
>   tal:attributes="href state/code;
>     selected python: test(state['code'] == request.get('state',
>         options.get('state'), 'selected')">
>    <span tal:replace="state/code"/>
>    <span tal:condition="state/long_name">:
>     <span tal:replace="state/long_name"/></span>
>  </option>
> </select>
> 
> Brutal, eh?  But we've probably all been there.  With a PI:
> 
> <?python
> state_sel = []
> for state in options['states']:
>     state_data = {}
>     if state['code'] == request.get('state', options.get('state')):
>         state_data['selected'] = 'selected'
>     state_data['description'] = state_data['code'] = state['code']
>     if state['long_name']:
>         state_data['description'] += ': ' + state['long_name']
>     state_sel.append(state_data)
> ?>
> <select name="state">
>  <option tal:repeat="state state_sel"
>   tal:attributes="value state/code selected state/selected | nothing"
>   tal:content="state/description">state</option>
> </select>
> 
> It's not any shorter, but it sure is easier to write, and keeps the 
> markup fairly clean.
> 
> Of course, in most environments there's ways to move this code elsewhere 
> -- into an external function or into the code that calls this template. 
>  But that turns what's actually a very localized bit of display-related 
> code into something else.  This doesn't actually *belong* in the 
> "controller"; the Python code is clearly part of the view.  But it's 
> also horribly ugly when put into the markup.
> 
> I think it's actually really good for ZPT's ideal of being friendly to 
> people with different roles -- the markup becomes simple enough for 
> someone who knows only HTML, and for those middling people (of which I 
> think there are many) who would be comfortable with Python but aren't 
> necessarily comfortable with adding code to a controller or a Python 
> script (code which probably has much different duties), it gives them an 
> easy transitional area.
> 
> Anyway, I think it's a nice idea, and would fit well into ZPT.
> 
> (I'd also love if ZPT did ${expr} substitution like Kid, but that's a 
> different issue)
> 

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