Model the mesh and background as dataclasses

Replace the hand-rolled Mesh class and the SimpleNamespace background
with dataclasses, and introduce PEP 695 type aliases for the geometry
primitives. No behavior change.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: realpython-bot

python315-sampling-profiler/src/pretzel/assets.py

@@ -1,15 +1,23 @@
 """Load Pretzel's model and background assets from disk."""
 
+from dataclasses import dataclass
 from importlib.resources import files
-from types import SimpleNamespace
 
 import numpy as np
+import numpy.typing as npt
 
 from pretzel.engine import Mesh
 
 ASSETS_DIR = files("pretzel") / "assets"
 
 
+@dataclass
+class Background:
+    name: str
+    path: str
+    pixels: npt.NDArray[np.float32]
+
+
 def asset_path(name):
     return str(ASSETS_DIR / name)
 
@@ -31,7 +39,7 @@ def load_mesh(name):
 def load_background(name, fast=False):
     path = asset_path(name)
     decode = decode_ppm if fast else decode_ppm_pixel_by_pixel
-    return SimpleNamespace(name=name, path=path, pixels=decode(path))
+    return Background(name=name, path=path, pixels=decode(path))
 
 
 def decode_ppm_pixel_by_pixel(path):

python315-sampling-profiler/src/pretzel/engine.py

@@ -1,12 +1,22 @@
 """Pure-Python 3D math: rotation, projection, culling, and sorting."""
 
 import math
+from dataclasses import dataclass
 
+type Vertex = tuple[float, float, float]
+type Face = tuple[int, int, int]
+type Point = tuple[float, float]
+type Matrix = tuple[
+    tuple[float, float, float],
+    tuple[float, float, float],
+    tuple[float, float, float],
+]
 
+
+@dataclass
 class Mesh:
-    def __init__(self, vertices, faces):
-        self.vertices = vertices
-        self.faces = faces
+    vertices: list[Vertex]
+    faces: list[Face]
 
 
 def rotation_matrix(pitch, yaw, roll):