Create a json tree from csv list in python

Question

I\'m trying to build a json hierarchy from a simple table in python.

The data comes in looking like the following:

id         parent          name
1          


        

Answer 1

To assign all child nodes to its parent, you can do two passes over the list of nodes. The first pass adds each node to a UserDict. In the second pass the parent of each node is guaranteed to be in the UserDict so the node can be added to the children of its parent.

To serialize to JSON a JSONEncoder can be used.

#!/usr/bin/env python

import sys
import json
import UserDict

class Node(object):
    def __init__(self, nid, parent, name):
        self.nid = nid
        self.parent = parent
        self.children = []
        self.name = name

class NodeDict(UserDict.UserDict):
    def addNodes(self, nodes):
        """ Add every node as a child to its parent by doing two passes."""
        for i in (1, 2):
            for node in nodes:
                self.data[node.nid] = node
                if node.parent in self.data.keys():
                    if node.parent != "none" and
                       node not in self.data[node.parent].children:
                        self.data[node.parent].children.append(node)

class NodeJSONEncoder(json.JSONEncoder):
    def default(self, node):
        if type(node) == Node:
            return {"nid":node.nid, "name":node.name, "children":node.children}
        raise TypeError("{} is not an instance of Node".format(node))

if __name__ == "__main__":
    nodes = []

    with open(sys.argv[1]) as f:
        for row in f.readlines()[1:]:
            nid, parent, name = row.split()
            nodes.append(Node(nid, parent, name))

    nodeDict = NodeDict()
    nodeDict.addNodes(nodes)

    rootNodes = [node for nid, node in nodeDict.items()
                 if node.parent == "none"]
    for rootNode in rootNodes:
        print NodeJSONEncoder().encode(rootNode)

Result:

{"name": "test-name-4", "nid": "4", "children":[
     {"name": "test-name-10", "nid": "10", "children":[
         {"name": "test-name-1", "nid": "1", "children":[
            {"name": "test-name-7", "nid": "7", "children": []},
            {"name": "test-name-8", "nid": "8", "children":[
                {"name": "test-name-9", "nid": "9", "children": []}]}]},
         {"name": "test-name-2", "nid": "2", "children": []},
         {"name": "test-name-5", "nid": "5", "children":[
             {"name": "test-name-3", "nid": "3", "children": []}]}]}]}
{"name": "test-name-6", "nid": "6", "children": []}