Convert tree to dictionary python

Question

I have a list of elements with attrs: parent, level, is_leaf_node, is_root_node, is_child_node.

I want to convert this list to hierarchy dict. Example of output dict:

{
        'Technology':
            {
             'Gadgets':{},
             'Gaming':{},
             'Programming':
                {
                    'Python':{},
                    'PHP':{},
                    'Ruby':{},
                    'C++':{}
                },
             'Enterprise':{},
             'Mac':{},
             'Mobile':{},
             'Seo':{},
             'Ui':{},
             'Virtual Worlds':{},
             'Windows':{},
            },
        'News':{
            'Blogging':{},
            'Economics':{},
            'Journalism':{},
            'Politics':{},
            'News':{}
            },}

I don't know algorithm. How to do it?

Given a list of lists, write a Python program to convert the given list of lists into a tree-like dictionary.

Examples:

Input : [[1], [2, 1], [3, 1], [4, 2, 1], [5, 2, 1], [6, 3, 1], [7, 3, 1]]
Output : {1: {2: {4: {}, 5: {}}, 3: {6: {}, 7: {}}}}

Input : [['A'], ['B', 'A'], ['C', 'A'], ['D', 'C', 'A']]
Output : {'A': {'C': {'D': {}}, 'B': {}}}

Method #1 : Naive Method
This is a Naive approach in which we use two for loops to traverse the list of lists. We initialize the empty dictionary ‘tree’ to currTree and each time we check if the key (list of list’s item) is included in the currTree or not. If not, include it in the currTree, otherwise do nothing. Finally, assign the currTree[key] to currTree.

def formTree(list):

tree = {}

for item in list:

currTree = tree

for key in item[::-1]:

if key not in currTree:

currTree[key] = {}

currTree = currTree[key]

return tree

lst = [['A'], ['B', 'A'], ['C', 'A'], ['D', 'C', 'A']]

print(formTree(lst))

Output:

{'A': {'B': {}, 'C': {'D': {}}}}

Method #2 : Using reduce()
The reduce() function is used to apply a particular function passed in its argument to all of the list elements mentioned in the sequence passed along. We will use reduce() to traverse the dictionary and reuse getTree() to find the location to store the value for setTree(). All but the last element in mapList is needed to find the ‘parent’ dictionary to add the value to, then use the last element to set the value to the right key.

from functools import reduce

from operator import getitem

def getTree(tree, mappings):

return reduce(getitem, mappings, tree)

def setTree(tree, mappings):

getTree(tree, mappings[:-1])[mappings[-1]] = dict()

lst = [['A'], ['B', 'A'], ['C', 'A'], ['D', 'C', 'A']]