Scene improvements

[einarf]

The current sprite_lists and name_mapping members are "public". Some users are modifying these directly causing issues that are hard to debug and understand. We should make them private and add additional tools if needed.

arcade/arcade/scene.py

Lines 30 to 32 in 98d4cac

	def __init__(self) -> None:
	self.sprite_lists: List[SpriteList] = []
	self.name_mapping: Dict[str, SpriteList] = {}

Things like __len__ and __delitem__ are candidates here.

On a few occations users have been deleting spritelists from name_mapping thinking that this will remove the spritelist. For more dynamic worlds this means you end up with hundres of spritelists in spritelists and performance tanks.

[einarf]

Another source of bugs is that add_sprite_list doesn't yell if you are adding a spritelist with an existing nane. It will overwrite the existing dict entry and append the spritelist to spritelists. This means games can easily lose track of spritelists and the game will grind to a halt over time.

We should also cover all these cases in unit tests.

[gran4]

You can't make things in python private. I think the best way to go about this is to give warnings and comments in the code. I am also trying to getting to detect when it is happening.

[einarf]

You can't make things in python private. I think the best way to go about this is to give warnings and comments in the code. I am also trying to getting to detect when it is happening.

I know. I guess non-public is a better word. Just starting the name with an underscore. Most programmers know this means you shouldn't really access it or that there might be some bad consequences for doing so. Trying to avoid this happening is usually not worth it. (PEP 8)

We do this everywhere in the arcade codebase.

[gran4]

@einarf I think you can close this.

[pushfoo]

Things like __len__ and __delitem__ are candidates here.

I'd like to take another look at this before closing.

[Cleptomania]

I think adding __len__ and __delitem__ would be good. They should be fairly easy to add so no reason not to.