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    <p>What you have here is a graph (probably just a tree) with connections between nodes represented by a <code>parent</code> key. This is known as an <a href="http://en.wikipedia.org/wiki/Adjacency_list" rel="nofollow">adjacency list</a>.</p> <p>You want to produce a tree structure with links to other nodes through a <code>children</code> key which is a list of other nodes.</p> <p>To convert an adjacency list into a tree, you first need to have a way to retrieve a node by its id, so the first step is to create a dict of every node, keyed by id.</p> <p>Then you have to go through the list again and add children to their parents.</p> <p>Finally, make a list of nodes without parents (the root nodes).</p> <p>Note that you don't need a recursive algorithm at all.</p> <p>We can combine some of these steps to avoid going through the list multiple times. Code below:</p> <pre><code>def nest_list(L): """Modify list of associative dicts into a graph and return roots of graph Association is via a 'parent' key indicating a corresponding 'id'. Items in the list *will be modified*. Children will be placed in a list for a 'children' key Items without children will have no 'children' key 'parent' keys will be removed. Returned list is the full list of items which are not children of any other items. """ idx = {} children = [] root = [] # first pass: index items by id # if the item has no parents, put it in the 'root' list # otherwise add it to the 'children' list which we will # process in a second pass for item in L: idx[item['id']] = item if 'parent' in item: children.append(item) else: root.append(item) # second pass: find the parents of our children for child in children: parent = idx[child['parent']] del child['parent'] try: # retrieve the list of children for this # parent childlist = parent['children'] except KeyError: # this item has received no children so far # so we need to make a 'children' key and list # for it. parent['children'] = childlist = [] # append this child to the parent's list of children childlist.append(child) #all done: return new root list return root </code></pre> <p>Code in action:</p> <pre><code>oldlist = [{ "name":"Folder 2", "id":"zRDg", "parent":"OY00", "type":"folder" }, { "name":"Folder 1", "id":"OY00", "type":"folder" }, { "name":"Folder 3", "id":"ZDE1", "type":"folder" }, { "name":"DX00025.jpg", "id":"9Xdd", "parent":"OY00", "type":"jpeg" }] expected = [{ "name":"Folder 1", "id":"OY00", "type":"folder", "children": [{ "name":"Folder 2", "id":"zRDg", "type":"folder" }, { "name":"DX00025.jpg", "id":"9Xdd", "type":"jpeg" }] }, { "name":"Folder 3", "id":"ZDE1", "type":"folder" }] from pprint import pprint newlist = nest_list(oldlist) pprint(newlist) assert newlist == expected </code></pre>
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    1. POSorting JSON object(s) into a Hierarchy
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    1. USFrancis Avila
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      1. VTUpMod
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    1. COBut what about folder withing folders withing folder and a real live dynamic Hierarchy, This example completely ignores folder 4 link: http://ideone.com/fkgYGx
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      1. USKivylius
    2. COBecause "Folder 4" is it's own parent! Do you really want to allow that? You could add a special case for `item['id'] == item['parent']`, but honestly I have no idea how that should be handled.
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      1. USFrancis Avila
    3. COMy silly mistake, wrong copy paste, sorry. this then successfully support nesting of items, what i dont get is how this works, where/how do's the nesting occur, you could have /folder/folder/folder/folder/file.jsp and this code seems to work but i dont understand where/how the nesting part occurs.
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