build_tree_from_flat.py

class Node:
    def __init__(self, key, data):
        self.key = key
        self.data = data
        self.children = []

    def display(self, level=0):
        tab = " " * (level * 3)
        print(tab + self.data)
        for child in self.children:
            child.display(level + 1)


paths = [
    {"key": 2, "data": "book", "path": "store/book", "parent_key": 1},
    {"key": 4, "data": "science", "path": "store/book/science", "parent_key": 2},
    {"key": 3, "data": "novel", "path": "store/book/novel", "parent_key": 2},
    {"key": 6, "data": "macbook", "path": "store/computer/macbook", "parent_key": 5},
    {"key": 1, "data": "store", "path": "store", "parent_key": None},
    {"key": 5, "data": "computer", "path": "store/computer", "parent_key": 1},
    {"key": 7, "data": "dell", "path": "store/computer/dell", "parent_key": 5},
]


def build_tree(flat):
    tree = {}

    flat.sort(key=lambda x: x["path"])

    visited = {}

    for item in flat:
        key = item["key"]
        node = Node(key, item["data"])
        visited[key] = node

        parent_key = item["parent_key"]
        if parent_key not in visited:
            tree = node

        else:
            parent = visited[parent_key]
            parent.children.append(node)

    return tree


tree = build_tree(paths)
tree.display()