gistfile1.txt

import pprint

def nested_tree(edges):

    nested = {}

    for from_, to in edges:
        value = {}


        if nested.get(from_):
            nested[from_][to]={}
        else:
            nested[from_] = value
            value[to]= {}

    pprint.pprint(nested)


if __name__ == '__main__':



    edges = [
    ['a', 'b'],
    ['a', 'f'],
    ['a', 'j'],
    ['b', 'c'],
    ['b', 'd'],
    ['d', 'e'],
    ['f', 'g'],
    ['g', 'h'],
    ['g', 'i'],
    ]

    nested_tree(edges)
    


# nested = {
#     'a': {
#         'b': {
#         'c': { },
#         'd': {
#             'e': { }
#             }
#         },
#         'f': {
#         'g': {
#             'h': { },
#             'i': { },
#             },
#         },
#         'j': { },
#         }
#     }