Generate nested list of children from recursive list of dict?

Question

I have information about a (simplified example) hierarchical taxonomy,

A - AA - AAA
A - AA - AAB

A - AB

B

I have data for it as a list of dicts in the following format:

[
{"name": "A",
"id": 10,
"path": ["A"]},

{"name": "AA",
"id": 7,
"path": ["A", "AA"]}

...

]

(the id is random)

I am trying to show it in a dash treeview widget based on AntD. It requires me to convert it to the following format:

[{"title": "A", "key": 10, "children": 
    [{"title": "AA", "key": 11, "children":
        [{...}] , 
    {"title": "AB", "key": 12},
    ...]},
{"title": "B", "key": 18}]

In other words, it's a recursive list of dicts, where there is a key called "children", which is another list of dicts taking on the same format.

I know I need to write a recursive function, but it's proving very tricky for me.

trincot · Accepted Answer · 2022-09-27 17:52:07Z

You could keep track of the nodes with a dictionary keyed by "title". Then for each element in a path, navigate through the tree, each time inserting into "children" when it is the first time that element is encountered:

def maketree(data):
    bytitle = {
        d["name"]: { "title": d["name"], "key": d["id"] }
        for d in data
    }
    
    root = { "children": [] }
    done = set()
    for node in data:
        current = root
        for title in node["path"]:
            if title not in done:
                done.add(title)
                if "children" not in current:
                    current["children"] = []
                current["children"].append(bytitle[title])
            current = bytitle[title]
    return root["children"]

// Example input and conversion
data = [
    {"name": "A",   "id": 10, "path": ["A"]},
    {"name": "AA",  "id": 7,  "path": ["A", "AA"]},
    {"name": "AAA", "id": 14, "path": ["A", "AA", "AAA"]},
    {"name": "AAB", "id": 12, "path": ["A", "AA", "AAB"]},
    {"name": "AB",  "id": 1,  "path": ["A", "AB"]},
    {"name": "B",   "id": 5,  "path": ["B"]},
]
tree = maketree(data)
print(tree)

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