diff -r 40f1b06ec989 Doc/library/stdtypes.rst
--- a/Doc/library/stdtypes.rst	Sun Dec 18 01:37:12 2016 +0000
+++ b/Doc/library/stdtypes.rst	Thu Dec 29 02:34:23 2016 -0800
@@ -2022,6 +2022,18 @@
    You can use :meth:`str.maketrans` to create a translation map from
    character-to-character mappings in different formats.
 
+   Another approach is to use **defaultdict** as translation table. Below example
+   keeps only lower case ASCII alphabets in a string::
+        
+        >>> from collections import defaultdict
+        >>> dd = defaultdict(lambda:None, {ord(ch):ch for ch in 'qwertyuiopasdfghjklzxcvbnm'})
+        >>> '1. Keep only lower case alphabets'.translate(dd)
+        'eeponlylowercasealphabets'
+
+   See :class:`collections.defaultdict` for more ways to create defaultdict.
+   Note that key in translate table should be an ordinal that is why
+   ``ord(ch)`` is used as key in defaultdict example.
+
    See also the :mod:`codecs` module for a more flexible approach to custom
    character mappings.