gistfile1.py

# Create dataset
people = [{'salary': i} for i in range(20000)]
for person in people:
  person['friends'] = [(i + person['salary']) % 20000 for i in range(10)]

# people = [..., {'salary': 12308, 'friends': [12308, 12309, 12310, 12311, 12312, 12313, 12314, 12315, 12316, 12317]}, ...]

for person in people:
  total_salary = 0
  for friend in person.nominated_friends:
    total_salary += friend.salary
    
  person.avg_salary_of_friends = total_salary ./ len(person.nominated_friends)