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devel / comp.lang.python / Re: Optional arguments in a class behave like class attributes.

Re: Optional arguments in a class behave like class attributes.

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From: ros...@gmail.com (Chris Angelico)
Newsgroups: comp.lang.python
Subject: Re: Optional arguments in a class behave like class attributes.
Date: Tue, 18 Oct 2022 01:57:13 +1100
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by: Chris Angelico - Mon, 17 Oct 2022 14:57 UTC

On Tue, 18 Oct 2022 at 01:39, Abderrahim Adrabi
<abderrahim.adrabi@gmail.com> wrote:
> 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
>

This makes the default be a single list, the same list for all of
them. If you want the default to be "construct a new list", you'll
need something else:

def __init__(self, games=None):
if games is None: games = []

There is an open proposal to allow this syntax, which would do what you want:

def __init__(self, games=>[]):

However, this is not part of any current version of Python.

ChrisA

Subject	Author
Re: Optional arguments in a class behave like class attributes.	Chris Angelico