Flat file to hierarchical tree - Python Way

import json

"""
"This class converts a flat file into a json hierarchical tree
"Inputs: a pandas data frame with flat file loaded
""""
class hierarchy_tree(object):
    def __init__(self, data, ):
        # self.__file = json_file_path
        self.__data = data
        self.__result = {'name':None, 'children':[], 'result':None}


    """
    Call this public function to convert a json flat file to json tree
    """
    def create(self, start=0, finish=None, callback=None):
        data = self.__data
        self.__callback = None
        # check if callback is a function
        if callable(callback):
            self.__callback = callback

        # iterate on each item
        for row in data.iterrows():
            #each row is a tuple
            if finish == None:
                finish = len(row[1])

            row = row[1][start:finish]
            lineage = []
            for x in range(len(row)):
                lineage.append(row[x])
            self.__build_path(lineage)
        return json.dumps(self.__result)

    """
        This function actually creates nested dictionary
        that is later dumped as json
    """
    def __build_path(self, lineage):
        parent = self.__result

        for item in lineage:
            # check if the current item exists as dictionary name
            index = -1
            for child in range(len(parent['children'])):
                if parent['children'][child]['name'] == item:
                    # reset index if item found
                    index = child
                    break
            # if existing item was not found
            if index == -1:
                # update as last item in dictionary
                parent['children'].append({'name':item, 'children':[], 'result':None})
            #
            # implement callback
            #pass arguments - Item text and its index in lineage
            #
            if callable(self.__callback):
                parent['children'][index]['result'] = self.__callback(lineage, lineage.index(item))
            # reset parent
            parent = parent['children'][index]

Example Usage:

def callbackfunc(list, index):
    return list[index] + str(index)

data = pandas.read_json(<json file path>)
tree = hierarchy_tree(data)
print tree.create(start=0, finish=3, callback=callbackfunc)