diff --git a/Lib/ntpath.py b/Lib/ntpath.py
index f9f6c78566e8ed..a8fa245857a7e3 100644
--- a/Lib/ntpath.py
+++ b/Lib/ntpath.py
@@ -32,12 +32,6 @@
            "samefile", "sameopenfile", "samestat", "commonpath", "isjunction",
            "isdevdrive"]
 
-def _get_bothseps(path):
-    if isinstance(path, bytes):
-        return b'\\/'
-    else:
-        return '\\/'
-
 # Normalize the case of a pathname and map slashes to backslashes.
 # Other normalizations (such as optimizing '../' away) are not done
 # (this is done by normpath).
@@ -108,8 +102,6 @@ def join(path, *paths):
         seps = '\\/'
         colon_seps = ':\\/'
     try:
-        if not paths:
-            path[:0] + sep  #23780: Ensure compatible data type even if p is null.
         result_drive, result_root, result_path = splitroot(path)
         for p in map(os.fspath, paths):
             p_drive, p_root, p_path = splitroot(p)
@@ -232,7 +224,7 @@ def split(p):
     Return tuple (head, tail) where tail is everything after the final slash.
     Either part may be empty."""
     p = os.fspath(p)
-    seps = _get_bothseps(p)
+    seps = b'\\/' if isinstance(p, bytes) else '\\/'
     d, r, p = splitroot(p)
     # set i to index beyond p's last slash
     i = len(p)
@@ -303,7 +295,7 @@ def ismount(path):
     """Test whether a path is a mount point (a drive root, the root of a
     share, or a mounted volume)"""
     path = os.fspath(path)
-    seps = _get_bothseps(path)
+    seps = b'\\/' if isinstance(path, bytes) else '\\/'
     path = abspath(path)
     drive, root, rest = splitroot(path)
     if drive and drive[0] in seps:
@@ -368,13 +360,15 @@ 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:
@@ -567,10 +561,8 @@ def normpath(path):
                     i += 1
             else:
                 i += 1
-        # If the path is now empty, substitute '.'
-        if not prefix and not comps:
-            comps.append(curdir)
-        return prefix + sep.join(comps)
+        path = prefix + sep.join(comps)
+        return path or curdir
 
 else:
     def normpath(path):
@@ -636,8 +628,9 @@ def _readlink_deep(path):
         allowed_winerror = 1, 2, 3, 5, 21, 32, 50, 67, 87, 4390, 4392, 4393
 
         seen = set()
-        while normcase(path) not in seen:
-            seen.add(normcase(path))
+        normp = normcase(path)
+        while normp not in seen:
+            seen.add(normp)
             try:
                 old_path = path
                 path = _nt_readlink(path)
@@ -651,6 +644,7 @@ def _readlink_deep(path):
                         path = old_path
                         break
                     path = normpath(join(dirname(old_path), path))
+                normp = normcase(path)
             except OSError as ex:
                 if ex.winerror in allowed_winerror:
                     break
@@ -720,7 +714,7 @@ def realpath(path, *, strict=False):
             prefix = b'\\\\?\\'
             unc_prefix = b'\\\\?\\UNC\\'
             new_unc_prefix = b'\\\\'
-            cwd = os.getcwdb()
+            getcwd = os.getcwdb
             # bpo-38081: Special case for realpath(b'nul')
             devnull = b'nul'
             if normcase(path) == devnull:
@@ -729,14 +723,14 @@ def realpath(path, *, strict=False):
             prefix = '\\\\?\\'
             unc_prefix = '\\\\?\\UNC\\'
             new_unc_prefix = '\\\\'
-            cwd = os.getcwd()
+            getcwd = os.getcwd
             # bpo-38081: Special case for realpath('nul')
             devnull = 'nul'
             if normcase(path) == devnull:
                 return '\\\\.\\NUL'
         had_prefix = path.startswith(prefix)
         if not had_prefix and not isabs(path):
-            path = join(cwd, path)
+            path = join(getcwd(), path)
         try:
             path = _getfinalpathname(path)
             initial_winerror = 0
diff --git a/Lib/posixpath.py b/Lib/posixpath.py
index b7fbdff20cac99..07073f26c94f09 100644
--- a/Lib/posixpath.py
+++ b/Lib/posixpath.py
@@ -38,12 +38,6 @@
            "commonpath", "isjunction","isdevdrive"]
 
 
-def _get_sep(path):
-    if isinstance(path, bytes):
-        return b'/'
-    else:
-        return '/'
-
 # Normalize the case of a pathname.  Trivial in Posix, string.lower on Mac.
 # On MS-DOS this may also turn slashes into backslashes; however, other
 # normalizations (such as optimizing '../' away) are not allowed
@@ -60,7 +54,7 @@ def normcase(s):
 def isabs(s):
     """Test whether a path is absolute"""
     s = os.fspath(s)
-    sep = _get_sep(s)
+    sep = b'/' if isinstance(s, bytes) else '/'
     return s.startswith(sep)
 
 
@@ -74,15 +68,13 @@ def join(a, *p):
     will be discarded.  An empty last part will result in a path that
     ends with a separator."""
     a = os.fspath(a)
-    sep = _get_sep(a)
+    sep = b'/' if isinstance(a, bytes) else '/'
     path = a
     try:
-        if not p:
-            path[:0] + sep  #23780: Ensure compatible data type even if p is null.
         for b in map(os.fspath, p):
-            if b.startswith(sep):
+            if b.startswith(sep) or not path:  # startswith ensures no mixing
                 path = b
-            elif not path or path.endswith(sep):
+            elif path.endswith(sep):
                 path += b
             else:
                 path += sep + b
@@ -101,7 +93,7 @@ def split(p):
     """Split a pathname.  Returns tuple "(head, tail)" where "tail" is
     everything after the final slash.  Either part may be empty."""
     p = os.fspath(p)
-    sep = _get_sep(p)
+    sep = b'/' if isinstance(p, bytes) else '/'
     i = p.rfind(sep) + 1
     head, tail = p[:i], p[i:]
     if head and head != sep*len(head):
@@ -161,7 +153,7 @@ def splitroot(p):
     else:
         # Precisely two leading slashes, e.g.: '//foo'. Implementation defined per POSIX, see
         # https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13
-        return empty, p[:2], p[2:]
+        return empty, sep + sep, p[2:]
 
 
 # Return the tail (basename) part of a path, same as split(path)[1].
@@ -169,7 +161,7 @@ def splitroot(p):
 def basename(p):
     """Returns the final component of a pathname"""
     p = os.fspath(p)
-    sep = _get_sep(p)
+    sep = b'/' if isinstance(p, bytes) else '/'
     i = p.rfind(sep) + 1
     return p[i:]
 
@@ -179,7 +171,7 @@ def basename(p):
 def dirname(p):
     """Returns the directory component of a pathname"""
     p = os.fspath(p)
-    sep = _get_sep(p)
+    sep = b'/' if isinstance(p, bytes) else '/'
     i = p.rfind(sep) + 1
     head = p[:i]
     if head and head != sep*len(head):
@@ -192,6 +184,7 @@ def dirname(p):
 
 def ismount(path):
     """Test whether a path is a mount point"""
+    path = os.fspath(path)
     try:
         s1 = os.lstat(path)
     except (OSError, ValueError):
@@ -202,7 +195,6 @@ def ismount(path):
         if stat.S_ISLNK(s1.st_mode):
             return False
 
-    path = os.fspath(path)
     if isinstance(path, bytes):
         parent = join(path, b'..')
     else:
@@ -231,12 +223,13 @@ def expanduser(path):
     do nothing."""
     path = os.fspath(path)
     if isinstance(path, bytes):
+        sep = b'/'
         tilde = b'~'
     else:
+        sep = '/'
         tilde = '~'
     if not path.startswith(tilde):
         return path
-    sep = _get_sep(path)
     i = path.find(sep, 1)
     if i < 0:
         i = len(path)
@@ -276,11 +269,8 @@ def expanduser(path):
         return path
     if isinstance(path, bytes):
         userhome = os.fsencode(userhome)
-        root = b'/'
-    else:
-        root = '/'
-    userhome = userhome.rstrip(root)
-    return (userhome + path[i:]) or root
+    userhome = userhome.rstrip(sep)
+    return (userhome + path[i:]) or sep
 
 
 # Expand paths containing shell variable substitutions.
@@ -358,7 +348,7 @@ def normpath(path):
             sep = '/'
             dot = '.'
             dotdot = '..'
-        if not path:
+        if not path or path == dot:
             return dot
         _, initial_slashes, path = splitroot(path)
         comps = path.split(sep)
@@ -388,11 +378,17 @@ def abspath(path):
     """Return an absolute path."""
     path = os.fspath(path)
     if isinstance(path, bytes):
-        if not path.startswith(b'/'):
-            path = join(os.getcwdb(), path)
+        sep = b'/'
+        curdir = b'.'
+        getcwd = os.getcwdb
     else:
-        if not path.startswith('/'):
-            path = join(os.getcwd(), path)
+        sep = '/'
+        curdir = '.'
+        getcwd = os.getcwd
+    if not path.startswith(sep):
+        if not path or path == curdir:
+            return getcwd()
+        path = join(getcwd(), path)
     return normpath(path)
 
 
@@ -558,10 +554,8 @@ def commonpath(paths):
     try:
         split_paths = [path.split(sep) for path in paths]
 
-        try:
-            isabs, = set(p[:1] == sep for p in paths)
-        except ValueError:
-            raise ValueError("Can't mix absolute and relative paths") from None
+        if len({p.startswith(sep) for p in paths}) != 1:
+            raise ValueError("Can't mix absolute and relative paths")
 
         split_paths = [[c for c in s if c and c != curdir] for s in split_paths]
         s1 = min(split_paths)
@@ -572,7 +566,7 @@ def commonpath(paths):
                 common = s1[:i]
                 break
 
-        prefix = sep if isabs else sep[:0]
+        prefix = sep if paths[0].startswith(sep) else sep[:0]
         return prefix + sep.join(common)
     except (TypeError, AttributeError):
         genericpath._check_arg_types('commonpath', *paths)
diff --git a/Lib/test/test_posixpath.py b/Lib/test/test_posixpath.py
index ff78410738022d..645fcebc26a151 100644
--- a/Lib/test/test_posixpath.py
+++ b/Lib/test/test_posixpath.py
@@ -56,6 +56,8 @@ def test_join(self):
         self.assertEqual(fn(b"/foo", b"bar", b"baz"),          b"/foo/bar/baz")
         self.assertEqual(fn(b"/foo/", b"bar/", b"baz/"),       b"/foo/bar/baz/")
 
+        self.assertEqual(fn("a", ""),          "a/")
+        self.assertEqual(fn("a", "", ""),      "a/")
         self.assertEqual(fn("a", "b"),         "a/b")
         self.assertEqual(fn("a", "b/"),        "a/b/")
         self.assertEqual(fn("a/", "b"),        "a/b")
diff --git a/Misc/NEWS.d/next/Core and Builtins/2024-04-07-19-03-53.gh-issue-117609.J-C6J2.rst b/Misc/NEWS.d/next/Core and Builtins/2024-04-07-19-03-53.gh-issue-117609.J-C6J2.rst
new file mode 100644
index 00000000000000..7932a390ac150a
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2024-04-07-19-03-53.gh-issue-117609.J-C6J2.rst	
@@ -0,0 +1 @@
+Speedup some functions in :mod:`os.path`.