Optional arguments in a class behave like class attributes.

[Abderrahim Adrabi]

Hi all,

I tried to create a class with some optional arguments as always, but this
time I used the default values to be lists, dictionaries, and object
references.

So, these default values behave like class attributes, here is a demo:

# Using a list -----------------------------
class GameOne:
  def __init__(self, games = []) -> None:
    self.games = games

h = GameOne()
h.games.append("List, the first round")

g = GameOne()
g.games.append("List, the second round")

k = GameOne()
print('Using a list', k.games)

# Using a dictionary --------------------------
class GameTwo:
  def __init__(self, games = {}) -> None:
    self.games = games

h = GameTwo()
h.games['1er'] = "Dictionary, the first round"

g = GameTwo()
g.games['2ed'] = "Dictionary, the second round"

k = GameTwo()
print('Using a dictionary', k.games)

# Using an object ------------------------------
class Bonus:
  def __init__(self) -> None:
    self.stages = []

class GameThree:
  def __init__(self, bonus = Bonus()) -> None:
    self.bonus = bonus

h = GameThree()
h.bonus.stages.append('Object, the first round')

g = GameThree()
g.bonus.stages.append('Object, the second round')

k = GameThree()
print('Using an object', k.bonus.stages)

# Results ----------------------------------------

Using a list ['List, the first round', 'List, the second round']
Using a dictionary {'1er': 'Dictionary, the first round', '2ed':
'Dictionary, the second round'}
Using an object ['Object, the first round', 'Object, the second round']

# Used Python versions ---------------------------

3.5.1 (default, Dec  9 2015, 14:41:32)
[GCC 5.2.0]

3.7.14 (default, Sep  8 2022, 00:06:44)
[GCC 7.5.0]

3.8.6 (default, Jan 29 2021, 17:38:16)
[GCC 8.4.1 20200928 (Red Hat 8.4.1-1)]

3.9.9 (main, Nov 20 2021, 21:30:06)
[GCC 11.1.0]

My question: Is this normal behavior?

Thanks.