Improve scene.py

arcade/scene.py

@@ -396,3 +396,11 @@ def draw_hit_boxes(
 
         for sprite_list in self._sprite_lists:
             sprite_list.draw_hit_boxes(color, line_thickness)
+
+    def __bool__(self) -> bool:
+        """Returns whether or not `_sprite_lists` contains anything"""
+        return bool(self._sprite_lists)
+
+    def __contains__(self, item: Union[str, SpriteList]) -> bool:
+        """True when `item` is in `_sprite_lists` or is a value in `_name_mapping`"""
+        return item in self._sprite_lists or item in self._name_mapping

tests/unit/scene/test_scene_dunder_methods.py

@@ -0,0 +1,67 @@
+import arcade
+import pytest
+
+
+def test_len():
+    scene = arcade.Scene()
+    scene.add_sprite_list("Player")
+
+    assert len(scene) == 1
+
+    scene.add_sprite_list("Walls")
+    scene.add_sprite_list("Coins")
+
+    assert len(scene) == 3
+
+
+def test_delitem():
+    scene = arcade.Scene()
+    scene.add_sprite_list("Walls")
+    scene.add_sprite_list("Player")
+    scene.add_sprite_list("Coins")
+    del scene["Player"]
+
+    with pytest.raises(KeyError):
+        scene["Player"]
+
+    del scene[scene._sprite_lists[0]]
+
+    with pytest.raises(KeyError):
+        scene["Walls"]
+
+    del scene[0]
+
+    with pytest.raises(KeyError):
+        scene["Coins"]
+
+
+def test_bool():
+    scene = arcade.Scene()
+    assert not scene
+
+    scene.add_sprite_list("Walls")
+    assert scene
+
+
+def test_contains():
+    scene = arcade.Scene()
+    assert "Walls" not in scene
+    assert None not in scene
+
+    walls_spriteList = arcade.SpriteList()
+    scene.add_sprite_list("Walls", use_spatial_hash=True, sprite_list=walls_spriteList)
+    assert "Walls" in scene
+
+    test_sprite = arcade.Sprite()
+    walls_spriteList.append(test_sprite)
+    assert walls_spriteList in scene
+
+    coins_spriteList = arcade.SpriteList()
+    scene.add_sprite_list("Coins", use_spatial_hash=True, sprite_list=coins_spriteList)
+    assert "Coins" in scene
+
+    test_sprite = arcade.Sprite()
+    coins_spriteList.append(test_sprite)
+    assert coins_spriteList in scene
+
+    assert None not in scene