How to convert each branch of a JSON tree into a list of items?

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I want to convert each branch of a JSON tree structure into a list of items in that branch. I want to do it using loops but I can't access the objects using indices. 

Example JSON:
{
    "Root": { "child1": "abc",
              "child2": "def",
              "child3": { "grandchild1": "nick",
                           "grandchild2": "Sam"
                        }
             }
 }

I want to traverse them and store them as following: 

list1 = ['Root', "child1", "abc"]
list2 = ['Root', "child2", "def"]
list3 = ['Root', "child3", "grandchild1", "nick",]
list4 = ['Root', "child3", "grandchild2", "sam",]

I read the JSON as follows: 

import json

with open('sample.json') as f:
    tree = json.load(f)

Problem: I wanted to loop through these items and append it to various lists but I can only access them through their keys like tree['Root'] would give Child1, 2, 3 and then tree['Root']['child3'] should give me the other two members. However, this method is not scalable in my use case where I have 1400 branches (pretty deep nested) in the JSON file and I want to create 1400 lists for them.

Any ideas how to do this efficiently?

python-3.x python json
1 Answers

Using yield from statement from Python 3.3+ and a recursive function:

tree = {
"Root": { "Child1": "abc",
          "Child2": "def",
          "Child3": { "grandchild1": "nick",
                      "grandchild2": "Sam"
                    }
         }
}

def walk_json(tree, path=[]):
    try:
        for root, child in tree.items():
            yield from walk_json(child, path + [root])
    except AttributeError: # in case .items() is not possible (on leaves)
        yield path + [tree]

list(walk_json(tree))

will output:

[['Root', 'Child1', 'abc'],
['Root', 'Child2', 'def'],
['Root', 'Child3', 'grandchild1', 'nick'],
['Root', 'Child3', 'grandchild2', 'Sam']]
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