input: Write a function to optimize a Python algorithm to find the greatest 2 numbers from a list of 10000 integers. The function should return a tuple containing the two largest numbers in the list. If the list has fewer than 2 elements, the function should return None.
  
  def get_greatest_2(items):
   if len(items) < 2:
   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
  
  assert get_greatest_2([1, 5, 3, 7, 4, 7, 8, 9, 2, 10, 6, 8]) == (10, 9)
  assert get_greatest_2([1, 2]) == (2, 1)
  assert get_greatest_2([3]) == None
  assert get_greatest_2([]) == None
output: def get_greatest_2(items):
      if len(items) < 2:
          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