Document actual string.punctuation value. (GH-12270)

diff --git a/Doc/library/string.rst b/Doc/library/string.rst
index 46b2bfc..c2f6522 100644
--- a/Doc/library/string.rst
+++ b/Doc/library/string.rst
@@ -56,8 +56,7 @@
 .. data:: punctuation
 
    String of ASCII characters which are considered punctuation characters
-   in the ``C`` locale.
-
+   in the ``C`` locale: ``!"#$%&'()*+,-./:;<=>?@[\]^_`{|}~``.
 
 .. data:: printable