gh-106318: Add examples for str.partition() method

Author: adorilson

Doc/library/stdtypes.rst

@@ -2329,6 +2329,15 @@ expression support in the :mod:`re` module).
    after the separator.  If the separator is not found, return a 3-tuple containing
    the string itself, followed by two empty strings.
 
+   For example:
+
+   .. doctest::
+
+      >>> 'Monty Python'.partition(' ')
+      ('Monty', ' ', 'Python')
+      >>> 'Monty Python'.partition('-')
+      ('Monty Python', '', '')
+
 
 .. method:: str.removeprefix(prefix, /)