Replacing loop variables requires time (when instantiating a wrapper)

Why can’t I instantiate this List wrapper in constant time? The list is already created (and not a generator), and I’m just saving it in my class. Lists are passed by reference, so please explain. I’m really confused, and can’t seem to find answers.

UPDATE: clearing the loop variables at the beginning of the loop offsets the time to there. But doesn’t solve the issue.

UPDATE 2: by extending the list I was able to avoid the time loss for clearing and generating the first half of the list again.

• Class:

  """
  List instantiate test
  """
  class List:
      """
      List wrapper
      """
      def __init__(self, a: list[Number]):
          self.list = a
  

• Main:

  from datetime import datetime, timedelta
  Number = int | float
  def main() -> None:
      generate_list: timedelta = timedelta()
      instantiate: timedelta = timedelta()
      size: int = 2 ** 25
      while True:
          start: datetime = datetime.now()
          lst: list[Number] = list(range(size, 0, -1))
          generate_list += datetime.now() - start
          print(f"Total time generating lists:            {generate_list}")
          start: datetime = datetime.now()
          _: List = List(lst)
          instantiate += datetime.now() - start
          print(f"Total time instantiating List wrappers: {instantiate}")
          size *= 2
  

• Output:

  Total time generating lists:            0:00:00.849742
  Total time instantiating List wrappers: 0:00:00.000019
  Total time generating lists:            0:00:02.465526
  Total time instantiating List wrappers: 0:00:00.300718
  Total time generating lists:            0:00:05.719437
  Total time instantiating List wrappers: 0:00:00.985957
  ...
  

• Main with clearing:

  def main() -> None:
      generate_list: timedelta = timedelta()
      instantiate: timedelta = timedelta()
      clearing: timedelta = timedelta()
      size: int = 2 ** 25
      lst: list[Number] = []
      lst_wrapper: List = None
      while True:
          start: datetime = datetime.now()
          lst.clear()
          lst_wrapper = None
          clearing += datetime.now() - start
          print(f"Total time clearing:                    {clearing}")
          start: datetime = datetime.now()
          lst = list(range(size, 0, -1))
          generate_list += datetime.now() - start
          print(f"Total time generating lists:            {generate_list}")
          start: datetime = datetime.now()
          lst_wrapper = List(lst)
          instantiate += datetime.now() - start
          print(f"Total time instantiating List wrappers: {instantiate}")
          size *= 2
  

• Output:

  Total time clearing:                    0:00:00.000005
  Total time generating lists:            0:00:00.825880
  Total time instantiating List wrappers: 0:00:00.000006
  Total time clearing:                    0:00:00.354571
  Total time generating lists:            0:00:02.449832
  Total time instantiating List wrappers: 0:00:00.000026
  Total time clearing:                    0:00:00.996483
  Total time generating lists:            0:00:05.796596
  Total time instantiating List wrappers: 0:00:00.000046
  

• Main with extending:

  def main() -> None:
      generate_list: timedelta = timedelta()
      instantiate: timedelta = timedelta()
      start: int = 2 ** 24
      end: int = 2 ** 25
      start_time: datetime = datetime.now()
      lst: list[Number] = list(range(0, -start, -1))
      generate_list += datetime.now() - start_time
      print(f"Total time generating lists:            {generate_list}")
      while True:
          start_time = datetime.now()
          lst.extend(range(-start, -end, -1))
          generate_list += datetime.now() - start_time
          print(f"Total time generating lists:            {generate_list}")
          start_time = datetime.now()
          _: List = List(lst)
          instantiate += datetime.now() - start_time
          print(f"Total time instantiating List wrappers: {instantiate}")
          start *= 2
          end *= 2
  

• Output:

  Total time generating lists:            0:00:00.514641
  Total time generating lists:            0:00:00.981933
  Total time instantiating List wrappers: 0:00:00.000005
  Total time generating lists:            0:00:01.851684
  Total time instantiating List wrappers: 0:00:00.000025
  Total time generating lists:            0:00:03.668982
  Total time instantiating List wrappers: 0:00:00.000030