input: Write a function to find the greatest two numbers from a list of 10000 integers. Return the two greatest numbers in the form of a tuple. If the list has fewer than two numbers, return the available numbers. If the list is empty, return an empty tuple.
  
  def get_greatest_2(items):
      if len(items) < 2:
          return tuple(items)
      elif not items:
          return ()
      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([2, 2, 2]) == (2, 2)
  assert get_greatest_2([5, 6]) == (6, 5)
  assert get_greatest_2([]) == ()
  assert get_greatest_2([1]) == (1,)
output: def get_greatest_2(items):
      if len(items) < 2:
          return tuple(items)
      elif not items:
          return ()
      max1 = max2 = float('-inf')
      for item in items:
          if item > max1:
              max1, max2 = item, max1
          elif item > max2:
              max2 = item
      return max1, max2