[Zope-dev] Confused about manipulating nested lists in DTML

[Martijn Pieters]

At 14:33 15/03/99 , skip@mojam.com wrote:
>
>I have a list of lists:
>
>    [['Washington', 'state'], ['Washington', 'state', 'Auburn'], ...]
>
>The first element has length two, the rest length three.  If I pass that to
>a DocumentTemplate instance as a parameter named "data" and manipulate it
>thus:
>
>    <!--#var "len(_['data'])"-->
>    <!--#var data-->
>    <!--#in data-->
>	<!--#var "len(_['sequence-item'])"--> <!--#var sequence-item-->
>	<!--#if "len(_['sequence-item']) == 2"-->
>	    <p><!--#var "_['sequence-item'][0]"-->
>	    <!--#in sequence-item-->
>		<!--#var sequence-item--><br>
>	    <!--#/in-->
>	<!--#/if-->
>    <!--#/in-->
>
>I get the following output:

<<SNIP>>

>*What* objects have lengths of 9 and 18?  The outer list is length 33.  The
>inner lists are all length 2 or 3.  Obviously I screwed up and misused
>len(), but how?
>

The function len() is not Python's len(), but Zope's len(), and it only
returns lengths on strings.... just count the number of characters in
"_['data']" and "len(_['sequence-item'])".

You *should* use _.len():
    <!--#var "_.len(data)"-->
    <!--#var data-->
    <!--#in data-->
	<!--#var "_.len(_['sequence-item'])"--> <!--#var sequence-item-->
	<!--#if "_.len(_['sequence-item']) == 2"-->
	    <p><!--#var "_['sequence-item'][0]"-->
	    <!--#in sequence-item-->
		<!--#var sequence-item--><br>
	    <!--#/in-->
	<!--#/if-->
    <!--#/in-->

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M.J. Pieters, Web Developer
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