old_contents: import unittest
  """
  Given an array of integers, return an index i such that sum(A[0..i-1]) == sum(A[i+1...n-1]).
  Input: -7 1 5 2 -4 3 0
  Output: 3
  """
  
  """
  DAMN!
  Approach:
  1. Compute the sum of the array first, total_sum
  2. Scan from left to right.
  3. Initialize leftSum to zero.
  4. leftSum = leftSum + arr[i]
  5. rightSum = sum - arr[i]
  6. If leftSum == rightSum, return i.
  """
  
  
  def find_equilibrium_index(list_of_numbers):
  
      total_sum = sum(list_of_numbers)
      left_sum = 0
  
      for i in range(len(list_of_numbers)):
          total_sum = total_sum - list_of_numbers[i]
          if left_sum == total_sum:
              return i
          left_sum += list_of_numbers[i]
  
      return -1
  
  
  class TestEquilibriumIndex(unittest.TestCase):
  
      def test_equilibrium_index(self):
          list_of_numbers = [-7, 1, 5, 2, -4, 3, 0]
          self.assertEqual(find_equilibrium_index(list_of_numbers), 3)
  
  
  if __name__ == '__main__':
      unittest.main()
  
new_contents: import unittest
  """
  Given an array of integers, return an index i such that sum(A[0..i-1]) == sum(A[i+1...n-1]).
  Input: -7 1 5 2 -4 3 0
  Output: 3
  """
  
  """
  DAMN!
  Approach:
  1. Compute the sum of the array first, total_sum
  2. Scan from left to right.
  3. Initialize leftSum to zero.
  4. leftSum = leftSum + arr[i]
  5. total_sum = total_sum - arr[i]
  6. If leftSum == total_sum, return i.
  """
  
  
  def find_equilibrium_index(list_of_numbers):
  
      total_sum = sum(list_of_numbers)
      left_sum = 0
  
      for i in range(len(list_of_numbers)):
          total_sum = total_sum - list_of_numbers[i]
          if left_sum == total_sum:
              return i
          left_sum += list_of_numbers[i]
  
      return -1
  
  
  class TestEquilibriumIndex(unittest.TestCase):
  
      def test_equilibrium_index(self):
          list_of_numbers = [-7, 1, 5, 2, -4, 3, 0]
          self.assertEqual(find_equilibrium_index(list_of_numbers), 3)
  
  
  if __name__ == '__main__':
      unittest.main()
  
subject: Fix typo in approach