User-defined Exceptions
=======================
-Programs may name their own exceptions by creating a new exception class.
-Exceptions should typically be derived from the :exc:`Exception` class, either
-directly or indirectly. For example::
+Programs may name their own exceptions by creating a new exception class (see
+:ref:`tut-classes` for more about Python classes). Exceptions should typically
+be derived from the :exc:`Exception` class, either directly or indirectly. For
+example::
>>> class MyError(Exception):
... def __init__(self, value):