use python to return json data of extjs treepanel -

i use python (django) extjs4.2, don't know how return json format data of extjs treepanel below:

[{     "text":"a",     "id": 1,     "leaf":false,     "parentid":0,     "root":4,     "children": [{         "text":"a_1",         "id":2,         "leaf":false,         "parentid":1,         "root":3,         "children": [{             "id":7,             "leaf":true,             "parentid":2,             "root":3,             "text":"a_1_1",             "children":[]         }]     }] }] 

please me, thanks.

the structure of tree pretty easy understand: it's nested list of node every node's children property tree self. 1 can represent follow:

class node(object):     def __init__(self, id, text, root='', parent=none):         self.text = text         self.id = id         self.root = root         self.parent = parent         self.children = []      def append_child(self, node):         if node not in self.children:             node.parent = self             self.children.append(node)      def remove_child(self, node):         if node in self.children:             node.parent = none             self.children.remove(node)      def parent_id(self):         return self.parent.id if self.parent not none else 0      def is_leaf(self):         return len(self.children) == 0      def to_dict(self):         children_dict = [child.to_dict() child in self.children]         return {              "id": self.id,              "root": self.root,              "text": self.text,              "leaf": self.is_leaf(),              "parentid": self.parent_id(),              "children": children_dict,          }      def to_json(self):         return json.dumps(self.to_dict)