diff -r 910a4b12c796 Doc/library/string.rst
--- a/Doc/library/string.rst	Mon Apr 30 22:43:46 2012 +0800
+++ b/Doc/library/string.rst	Mon Apr 30 18:16:32 2012 +0200
@@ -91,8 +91,8 @@
 
    .. method:: format(format_string, *args, **kwargs)
 
-      :meth:`format` is the primary API method.  It takes a format template
-      string, and an arbitrary set of positional and keyword argument.
+      :meth:`format` is the primary API method.  It takes a format string and
+      an arbitrary set of positional and keyword arguments.
       :meth:`format` is just a wrapper that calls :meth:`vformat`.
 
    .. method:: vformat(format_string, args, kwargs)
@@ -101,8 +101,8 @@
       separate function for cases where you want to pass in a predefined
       dictionary of arguments, rather than unpacking and repacking the
       dictionary as individual arguments using the ``*args`` and ``**kwds``
-      syntax.  :meth:`vformat` does the work of breaking up the format template
-      string into character data and replacement fields.  It calls the various
+      syntax.  :meth:`vformat` does the work of breaking up the format string
+      into character data and replacement fields.  It calls the various
       methods described below.
 
    In addition, the :class:`Formatter` defines a number of methods that are
@@ -173,7 +173,8 @@
 
       Converts the value (returned by :meth:`get_field`) given a conversion type
       (as in the tuple returned by the :meth:`parse` method).  The default
-      version understands 'r' (repr) and 's' (str) conversion types.
+      version understands 's' (str), 'r' (repr) and 'a' (ascii) conversion
+      types.
 
 
 .. _formatstrings:
diff -r 910a4b12c796 Lib/string.py
--- a/Lib/string.py	Mon Apr 30 22:43:46 2012 +0800
+++ b/Lib/string.py	Mon Apr 30 18:16:32 2012 +0200
@@ -220,12 +220,14 @@
 
     def convert_field(self, value, conversion):
         # do any conversion on the resulting object
-        if conversion == 'r':
-            return repr(value)
+        if conversion is None:
+            return value
         elif conversion == 's':
             return str(value)
-        elif conversion is None:
-            return value
+        elif conversion == 'r':
+            return repr(value)
+        elif conversion == 'a':
+            return ascii(value)
         raise ValueError("Unknown conversion specifier {0!s}".format(conversion))
 
 
diff -r 910a4b12c796 Lib/test/test_string.py
--- a/Lib/test/test_string.py	Mon Apr 30 22:43:46 2012 +0800
+++ b/Lib/test/test_string.py	Mon Apr 30 18:16:32 2012 +0200
@@ -38,6 +38,13 @@
         self.assertEqual(fmt.format("{0!s}", 'test'), 'test')
         self.assertRaises(ValueError, fmt.format, "{0!h}", 'test')
 
+        # issue13579
+        self.assertEqual(fmt.format("{0!a}", 42), '42')
+        self.assertEqual(fmt.format("{0!a}",  string.ascii_letters),
+            "'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'")
+        self.assertEqual(fmt.format("{0!a}",  chr(255)), "'\\xff'")
+        self.assertEqual(fmt.format("{0!a}",  chr(256)), "'\\u0100'")
+
     def test_name_lookup(self):
         fmt = string.Formatter()
         class AnyAttr: