input: Write a function to find the greatest 2 numbers from a list of 10000 integers. If the list has less than 2 elements, return None.
  def get_greatest_2(items):
   max1 = max2 = float('-inf')
   for item in items:
   if item > max1:
   max1, max2 = item, max1
   elif item > max2:
   max2 = item
   return (max1, max2) if len(items) > 1 else None
  
  myList = [1, 5, 3, 7, 4, 7, 8, 9, 2, 10, 6, 8]
  assert get_greatest_2(myList) == (10, 9)
  myList = [1]
  assert get_greatest_2(myList) == None
  myList = [10, 20]
  assert get_greatest_2(myList) == (20, 10)
  myList = []
  assert get_greatest_2(myList) == 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)