Simplify ptrdiff getter, move tasks out of actual preamble

src/ctypesgen/printer_python/preamble.py

@@ -1,24 +1,11 @@
-# TODO
-# - add c_ptrdiff_t only on as-needed basis
-# - Avoid ctypes glob import (pollutes namespace)
-
 import ctypes
 from ctypes import *  # noqa: F401, F403
 
 def _get_ptrdiff_t():
-
-    int_types = (ctypes.c_int16, ctypes.c_int32)
+    int_types = [ctypes.c_int16, ctypes.c_int32]
+    # Some builds of ctypes do not provide c_int64. Assumably, this means the platform doesn't have 64-bit pointers.
     if hasattr(ctypes, "c_int64"):
-        # Some builds of ctypes apparently do not have ctypes.c_int64
-        # defined; it's a pretty good bet that these builds do not
-        # have 64-bit pointers.
-        int_types += (ctypes.c_int64,)
-
-    c_ptrdiff_t = None
-    for t in int_types:
-        if ctypes.sizeof(t) == ctypes.sizeof(ctypes.c_size_t):
-            c_ptrdiff_t = t
-
-    return c_ptrdiff_t
+        int_types.append(ctypes.c_int64)
+    return next((t for t in int_types if sizeof(t) == sizeof(c_size_t)), None)
 
 c_ptrdiff_t = _get_ptrdiff_t()

src/ctypesgen/printer_python/printer.py

@@ -14,7 +14,6 @@
 DEFAULTHEADER_PATH = THIS_DIR/"defaultheader.py"
 LIBRARYLOADER_PATH = CTYPESGEN_DIR/"libraryloader.py"
 
-
 # Concerning newlines handling, please read docs/dev_comments.md
 
 def ParagraphCtxFactory(file):
@@ -107,6 +106,9 @@ def print_info(self, argv):
 
 
     def print_templates(self, opts, outpath):
+        # TODO(preamble)
+        # - Perspectively, we'd like to add individual templates only on as-needed basis.
+        # - The ctypes * import is somewhat unfortunate for the namespace. On the other hand, prefixing would make the output bigger and less readable.
         if opts.embed_preamble:
             self._embed_file(PREAMBLE_PATH, "preamble")
             if opts.library: