old_contents: """
  Multiples of 3 and 5
  ====================
  
  If we list all the natural numbers below 10 that are multiples of
  3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.
  
  Find the sum of all the multiples of 3 or 5 below 1000.
  
  https://projecteuler.net/problem=1
  """
  
  
  is_multiple_of_3_or_5 = lambda n: n % 3 == 0 or n % 5 == 0
  print(sum([n for n in range(1, 1000) if is_multiple_of_3_or_5(n)]))
  
new_contents: """
  Multiples of 3 and 5
  ====================
  
  If we list all the natural numbers below 10 that are multiples of
  3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.
  
  Find the sum of all the multiples of 3 or 5 below 1000.
  
  https://projecteuler.net/problem=1
  """
  print(sum([n for n in range(1, 1000) if n % 3 == 0 or n % 5 == 0]))
  
subject: remove unnecessary lambda