input: Write a function to optimize a Python algorithm that finds the greatest 2 numbers from a list of 10000 integers. The function should return a tuple of the two greatest numbers. If the list is empty, it should return None.
  
  
  def get_greatest_2(items):
      if not items:
          return None
      max1 = max2 = float('-inf')
      for item in items:
          if item > max1:
              max1, max2 = item, max1
          elif item > max2:
              max2 = item
      return max1, max2
  
  myList = [1, 5, 3, 7, 4, 7, 8, 9, 2, 10, 6, 8]
  assert get_greatest_2(myList) == (10, 9)
  assert get_greatest_2([5, 4, 3, 2, 1]) == (5, 4)
  assert get_greatest_2([7, 7, 7, 7]) == (7, 7)
  assert get_greatest_2([]) == None
  
output: def get_greatest_2(items):
      if not items:
          return None
      max1 = max2 = float('-inf')
      for item in items:
          if item > max1:
              max1, max2 = item, max1
          elif item > max2:
              max2 = item
      return max1, max2