docs: Improve docs for os.path.commonprefix
diff --git a/Doc/library/os.path.rst b/Doc/library/os.path.rst
index e4fe44e..041277c 100644
--- a/Doc/library/os.path.rst
+++ b/Doc/library/os.path.rst
@@ -82,8 +82,21 @@
Return the longest path prefix (taken character-by-character) that is a
prefix of all paths in *list*. If *list* is empty, return the empty string
- (``''``). Note that this may return invalid paths because it works a
- character at a time. To obtain a valid path, see :func:`commonpath`.
+ (``''``).
+
+ .. note::
+
+ This function may return invalid paths because it works a
+ character at a time. To obtain a valid path, see
+ :func:`commonpath`.
+
+ ::
+
+ >>> os.path.commonprefix(['/dir1/dir2', '/dir3/dir4'])
+ '/dir'
+
+ >>> os.path.commonpath(['/dir1/dir2', '/dir3/dir4'])
+ '/'
.. function:: dirname(path)