Utilities for working with lists of model instances which represent trees.
Creates an iterator which returns (previous, current, next) triples, with
Nonefilling in when there is no previous or next available.
tree_item_iterator(items, ancestors=False, callback=<class 'str'>)¶
Given a list of tree items, iterates over the list, generating two-tuples of the current tree item and a
dictcontaining information about the tree structure around the item, with the following keys:
Trueif the current item is the start of a new level in the tree,
- A list of levels which end after the current item. This will be an empty list if the next item is at the same level as the current item.
True, the following key will also be available:
A list of representations of the ancestors of the current node, in descending order (root node first, immediate parent last).
For example: given the sample tree below, the contents of the list which would be available under the
'ancestors'key are given on the right:
Books ->  Sci-fi -> ['Books'] Dystopian Futures -> ['Books', 'Sci-fi']
You can overload the default representation by providing an optional
callbackfunction which takes a single argument and performs coercion as required.
drilldown_tree_for_node(node, rel_cls=None, rel_field=None, count_attr=None, cumulative=False, all_descendants=False)¶
Creates a drilldown tree for the given node. A drilldown tree consists of a node’s ancestors, itself and its immediate children or all descendants, all in tree order.
Optional arguments may be given to specify a
Modelclass which is related to the node’s class, for the purpose of adding related item counts to the node’s children:
Modelclass which has a relation to the node’s class.
- The name of the field in
rel_clswhich holds the relation to the node’s class.
- The name of an attribute which should be added to each child in
the drilldown tree, containing a count of how many instances
rel_clsare related through
True, the count will be for each child and all of its descendants, otherwise it will be for each child itself.
True, return all descendants, not just immediate children.
Takes a list/queryset of model objects in MPTT left (depth-first) order and caches the children and parent on each node. This allows up and down traversal through the tree without the need for further queries. Use cases include using a recursively included template or arbitrarily traversing trees.
NOTE: nodes _must_ be passed in the correct (depth-first) order. If they aren’t, a ValueError will be raised.
Returns a list of top-level nodes. If a single tree was provided in its entirety, the list will of course consist of just the tree’s root node.
For filtered querysets, if no ancestors for a node are included in the queryset, it will appear in the returned list as a top-level node.
Aliases to this function are also available:
- Use for recursive rendering in templates.
- Useful for chaining with queries; e.g., Node.objects.filter(**kwargs).get_cached_trees()