Improve documentation of new lazy loading system

docs/reST/ref/sndarray.rst

@@ -23,6 +23,8 @@ Each sample is an 8-bit or 16-bit integer, depending on the data format. A
 stereo sound file has two values per sample, while a mono sound file only has
 one.
 
+.. versionchanged:: 2.5.3 sndarray module is lazily loaded
+
 .. function:: array
 
    | :sl:`copy Sound samples into an array`

docs/reST/ref/surfarray.rst

@@ -35,6 +35,8 @@ pixels from the surface and any changes performed to the array will make changes
 in the surface. As this last functions share memory with the surface, this one
 will be locked during the lifetime of the array.
 
+.. versionchanged:: 2.5.3 surfarray module is lazily loaded
+
 .. function:: array2d
 
    | :sl:`Copy pixels into a 2d array`

src_py/__init__.py

@@ -264,17 +264,32 @@ def PixelArray(surface):  # pylint: disable=unused-argument
 
 # lastly, the "optional" pygame modules
 
+# Private, persisting alias for use in __getattr__
 _MissingModule = MissingModule
 
 
 def __getattr__(name):
+    """Implementation of lazy loading for some optional pygame modules.
+
+    The surfarray and sndarray submodules use numpy, so they are loaded
+    lazily to avoid a heavy numpy import if the modules are never used.
+
+    The first access of a lazily loaded submodule loads it and sets it
+    as an attribute on the pygame module. Pygame itself doesn't import these modules.
+    If the first access is an attribute access and not an import, then __getattr__ is
+    invoked (as the attribute isn't set yet), which imports the module dynamically.
+
+    All lazy submodules are directly referenced in the packager_imports function.
+    """
     from importlib import import_module
 
     LAZY_MODULES = "surfarray", "sndarray"
     if name not in LAZY_MODULES:
+        # Normal behavior for attribute accesses that aren't lazy modules
         raise AttributeError(f"module '{__name__}' has no attribute '{name}'")
     try:
         module = import_module(f"{__name__}.{name}")
+        # A successful import automatically sets the module attribute on the package
     except (ImportError, OSError):
         module = _MissingModule(name, urgent=0)
         globals()[name] = module