pythonGH-112727: Speed up pathlib.Path.absolute()

Use `_from_parsed_parts()` to create a pre-joined/pre-parsed path, rather
than passing multiple arguments to `with_segments()`

Lib/pathlib.py

@@ -1415,21 +1415,28 @@ def absolute(self):
         """
         if self.is_absolute():
             return self
-        elif self.drive:
-            # There is a CWD on each drive-letter drive.
-            cwd = os.path.abspath(self.drive)
-        else:
+        elif self.root:
             cwd = os.getcwd()
-            # Fast path for "empty" paths, e.g. Path("."), Path("") or Path().
-            # We pass only one argument to with_segments() to avoid the cost
-            # of joining, and we exploit the fact that getcwd() returns a
-            # fully-normalized string by storing it in _str. This is used to
-            # implement Path.cwd().
-            if not self.root and not self._tail:
-                result = self.with_segments(cwd)
-                result._str = cwd
-                return result
-        return self.with_segments(cwd, self)
+            if self._tail:
+                cwd_drv = os.path.splitroot(cwd)[0]
+                return self._from_parsed_parts(cwd_drv, self.root, self._tail)
+        else:
+            cwd = os.path.abspath(self.drive) if self.drive else os.getcwd()
+            if self._tail:
+                # Optimization: use os.path.splitroot() rather than _parse_path().
+                # This is possible because os.getcwd() returns a normalized path.
+                cwd_drv, cwd_root, cwd_tail = os.path.splitroot(cwd)
+                if cwd_tail:
+                    cwd_tail = cwd_tail.split(self.pathmod.sep)
+                    cwd_tail.extend(self._tail)
+                else:
+                    cwd_tail = self._tail
+                return self._from_parsed_parts(cwd_drv, cwd_root, cwd_tail)
+        # Optimization: store the result of os.getcwd() as the normalized
+        # string representation of the path.
+        result = self.with_segments(cwd)
+        result._str = cwd
+        return result
 
     def resolve(self, strict=False):
         """

Misc/NEWS.d/next/Library/2023-12-04-21-30-34.gh-issue-112727.jpgNRB.rst

@@ -0,0 +1 @@
+Speed up :meth:`pathlib.Path.absolute`. Patch by Barney Gale.