hierarchical unordered list from 'flat' dictionary of folder structure

Question

On the backend, i am getting a folder structure from an API. I recursively iterate over this structure to get all folders. These are then all stored in a 'flat' ordered dictionary. Each folder is stored with some properties to define the structure, the id of the parent folder, the amount of subfolders it has and if itself is a subnode or not.

Now from this ordered dict I am trying to make a nice hierarchical view with Genshi, but the furthest I've gotten so far is the template below. This results in only 2 levels, the root level, and one level below. Any folder even deeper will be displayed at the second level.

I am trying to do this without having to resort to doing a lot of relation checking on the initial parsing of the data to get the level a folder is at and stuff. Does anyone have any clever ideas?

<body>
  <div class="main_content">
    <h1>Catalogue Tree</h1>
    <ul>
      <li py:for="nodeId, nodeProps in nodes.iteritems()">
        <a py:if="nodeProps['SubNode'] == False" href="${tg.url('/node/' + nodeId)}">${nodeProps['Name']}</a>
        <py:if test="nodeProps['SubNode'] == True">
          <ul>
            <a href="${tg.url('/node/' + nodeId)}">${nodeProps['Name']}</a>
          </ul>
        </py:if>
      </li>
    </ul>
  </div>
</body>

Do your data nodes have parent->child links, or only child->parent? With the former, you could define a recursive template function to expand them, but if you don't have an easy way to get all of a parent's children, it will be harder. — Blckknght, May 18 '14 at 22:46
In the original api the xml structure is actually nested so I can easily add the parent>child links. But I'm not sure how proceed after that. Can you elaborate? — Sartsj, May 19 '14 at 06:39
I'd use `py:def` to define a "macro" that outputs the link to an node and then, if the node has children, creates a nested list and recursively calls itself to render each child node. I don't have `genshi` on my system, so I can't really make an answer that I know will work, but hopefully the suggestion is enough to get you on the right path. — Blckknght, May 19 '14 at 14:32
Your suggestion was indeed the way to go! I actually split up the root nodes from all the other nodes first (not sure now if that was necessary though), so I pass on 2 dicts to the template. Then in the template I indeed used `py:def` to generate a macro that also calls on itself to iterate over the subnodes. This is great! Thanks! See the code at http://pastie.org/9190171 Maybe you can post this as an answer so I can upvote it for you, since you did come up with the whole idea after all! — Sartsj, May 19 '14 at 17:15

Blckknght · Accepted Answer · 2014-05-19T22:48:59.643

As I commented, you can solve your issue with a recursive macro created with the py:def directive. Here's my attempt at a solution (note, I don't have genshi installed on my system, so this is untested):

<ul py:def="display_nodes(node_ids)">
    <li py:for="node_id in node_ids">
        <a href="${tg.url('/node/' + node_id)}">${nodes[node_id]['Name']}</a>
        <py:if test="nodes[node_id]['SubNodes']">
             ${display_nodes(nodes[node_id]['SubNodes'])}
        </py:if>
    </li>
</ul>
${display_nodes(root_nodes)}

This part of the template expects two parameters to be passed, a nodes dictionary that has all the nodes in it, and a root_nodes sequence that includes the IDs of all the top level nodes. The structure this creates is a little different than what the code you've linked to does, as it includes the list of child nodes in the <li> tag of their parent. I'm not sure if that makes any difference or not in the rendering, but it seemed most correct to me to do it that way.

Awesome, thanks! That's even better, a lot more efficient, it displays more nicely and it also made me clean up my code better on the backend :) There's just one small typo in your solution, you're declaring `node_ids` in the `py:def` but using `nodes_ids` in the `for` loop. — Sartsj, May 19 '14 at 22:15
I'm glad it helped. I've fixed the `nodes_ids` typo (a holdover from calling the argument `nodes` in an earlier draft of the code). — Blckknght, May 19 '14 at 22:49

hierarchical unordered list from 'flat' dictionary of folder structure

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