gh-117686: Improve the performance of ntpath.expanduser() (#117690)

Refactor out _get_bothseps() call from the loop.

Lib/ntpath.py

@@ -368,13 +368,15 @@ def expanduser(path):
     If user or $HOME is unknown, do nothing."""
     path = os.fspath(path)
     if isinstance(path, bytes):
+        seps = b'\\/'
         tilde = b'~'
     else:
+        seps = '\\/'
         tilde = '~'
     if not path.startswith(tilde):
         return path
     i, n = 1, len(path)
-    while i < n and path[i] not in _get_bothseps(path):
+    while i < n and path[i] not in seps:
         i += 1
 
     if 'USERPROFILE' in os.environ:

Misc/NEWS.d/3.13.0a6.rst

@@ -4,7 +4,7 @@
 .. release date: 2024-04-09
 .. section: Core and Builtins
 
-Improve performance of :func:`os.path.join`.
+Improve performance of :func:`os.path.join` and :func:`os.path.expanduser`.
 
 ..