account_id | parent_id
------------------------
5555       | None (пустой)

account_id | parent_id
-----------------------
6666       | 5555

# -*- coding: utf-8 -*-

import psycopg2
import psycopg2.extras

sql = "select * from accounts"


try:
    conn = psycopg2.connect("dbname='DB' user='postgres'"
                            " host='postgres.contora.com' password='xxxxxxxx'")
except psycopg2.Error as err:
    print("Connection error: {}".format(err))

try:
    cur = conn.cursor(cursor_factory=psycopg2.extras.RealDictCursor)
    cur.execute(sql)
    data = cur.fetchall()
except psycopg2.Error as err:
    print("Query error: {}".format(err))

data_dict = []
for row in data:
    data_dict.append(dict(row))


start_count = 0

for data_dict[start_count] in data_dict:
    ib_level = 0
    if data_dict[start_count].get('parent_id') is None:
        data_dict[start_count].update({'IB_level': ib_level})
        print('IB level 0:n')
        print(data_dict[start_count])
    elif isinstance(data_dict[start_count].get('parent_id'), int):
        ib_level_calc = ib_level + 1
        data_dict[start_count].update({'IB_level': ib_level_calc})
        print('IB level 1:n')
        print(data_dict[start_count])
    start_count = start_count + 1