Tutorial

Create a basic model for your tree. In this example we’ll use a Materialized Path tree:

from django.db import models
from treebeard.mp_tree import MP_Node

class Category(MP_Node):
    name = models.CharField(max_length=30)

    node_order_by = ['name']

    def __unicode__(self):
        return 'Category: %s' % self.name

Run syncdb:

$ python manage.py syncdb

Let’s create some nodes:

>>> from treebeard_tutorial.models import Category
>>> get = lambda node_id: Category.objects.get(pk=node_id)
>>> root = Category.add_root(name='Computer Hardware')
>>> node = get(root.pk).add_child(name='Memory')
>>> get(node.pk).add_sibling(name='Hard Drives')
<Category: Category: Hard Drives>
>>> get(node.pk).add_sibling(name='SSD')
<Category: Category: SSD>
>>> get(node.pk).add_child(name='Desktop Memory')
<Category: Category: Desktop Memory>
>>> get(node.pk).add_child(name='Laptop Memory')
<Category: Category: Laptop Memory>
>>> get(node.pk).add_child(name='Server Memory')
<Category: Category: Server Memory>

Note

Why retrieving every node again after the first operation? Because django-treebeard uses raw queries for most write operations, and raw queries don’t update the django objects of the db entries they modify. See: Known Caveats.

We just created this tree:

digraph introduction_digraph {
"Computer Hardware";
"Computer Hardware" -> "Hard Drives";
"Computer Hardware" -> "Memory";
"Memory" -> "Desktop Memory";
"Memory" -> "Laptop Memory";
"Memory" -> "Server Memory";
"Computer Hardware" -> "SSD";
}

You can see the tree structure with code:

>>> Category.dump_bulk()
[{'id': 1, 'data': {'name': u'Computer Hardware'},
  'children': [
     {'id': 3, 'data': {'name': u'Hard Drives'}},
     {'id': 2, 'data': {'name': u'Memory'},
      'children': [
         {'id': 5, 'data': {'name': u'Desktop Memory'}},
         {'id': 6, 'data': {'name': u'Laptop Memory'}},
         {'id': 7, 'data': {'name': u'Server Memory'}}]},
     {'id': 4, 'data': {'name': u'SSD'}}]}]
>>> Category.get_annotated_list()
[(<Category: Category: Computer Hardware>,
  {'close': [], 'level': 0, 'open': True}),
 (<Category: Category: Hard Drives>,
  {'close': [], 'level': 1, 'open': True}),
 (<Category: Category: Memory>,
  {'close': [], 'level': 1, 'open': False}),
 (<Category: Category: Desktop Memory>,
  {'close': [], 'level': 2, 'open': True}),
 (<Category: Category: Laptop Memory>,
  {'close': [], 'level': 2, 'open': False}),
 (<Category: Category: Server Memory>,
  {'close': [0], 'level': 2, 'open': False}),
 (<Category: Category: SSD>,
  {'close': [0, 1], 'level': 1, 'open': False})]

Read the treebeard.models.Node API reference for detailed info.