diff -r 00754d360e58 pep-0008.txt
--- a/pep-0008.txt	Wed Oct 23 19:49:13 2013 +0200
+++ b/pep-0008.txt	Thu Oct 24 09:26:42 2013 -0400
@@ -580,6 +580,10 @@
 standards, but where an existing library has a different style,
 internal consistency is preferred.
 
+Names that are visible to the user as public parts of the API should
+follow conventions that reflect usage rather than implementation.
+
+
 Descriptive: Naming Styles
 --------------------------
 
@@ -676,8 +680,21 @@
 Class Names
 ~~~~~~~~~~~
 
-Almost without exception, class names use the CapWords convention.
-Classes for internal use have a leading underscore in addition.
+Class names should normally use the CapWords convention, with classes
+intended solely for internal use starting with a leading underscore.
+
+This guideline should always be followed for abstract base classes,
+any other class where inheritance is encouraged or permitted, or
+*class-like* behavior and usage is the primary intent.
+
+In cases where inheritance is discouraged, or the class is primarily
+intended to be used "as is", the naming convention for callables
+(e.g. lower_case_with_underscores) may be used if it improves
+readability at the point of use.
+
+Note that there is a separate convention for builtin names: most builtin
+names are single words (or two words run together), with the CapWords
+convention used only for exception names and builtin constants.
 
 Exception Names
 ~~~~~~~~~~~~~~~