Index: reference/simple_stmts.rst
===================================================================
--- reference/simple_stmts.rst	(revision 74452)
+++ reference/simple_stmts.rst	(working copy)
@@ -156,6 +156,27 @@
   assignment, it raises an exception (usually but not necessarily
   :exc:`AttributeError`).
 
+  If the object is a class instance and the attribute
+  reference occurs on both sides of the assignment operator; for example::
+
+     self.x = self.x + 1
+
+  ... in the RHS expression, ``self.x`` is evaluated with
+  :meth:`getattr`, which can access either an instance attribute or (if
+  no instance attribute exists) a class attribute. The LHS target
+  ``self.x`` is assigned with :meth:`setattr`, which *always* accesses
+  an instance attribute, creating it if necessary. Thus, the two
+  occurrences of ``self.x`` do not necessarily refer to the same
+  variable: if the RHS expression refers to a class attribute, the LHS
+  creates a new instance attribute as the target of the assignment.
+  (This description does not necessarily
+  apply to attributes defined with :meth:`property`, which are accessed
+  with user-defined functions instead of 
+  :meth:`getattr` and :meth:`setattr`).
+
+  See section :ref:`augassign` for a similar note on
+  attribute references.
+
   .. index::
      pair: subscription; assignment
      object: mutable
@@ -253,7 +274,7 @@
 *in-place* behavior, the binary operation performed by augmented assignment is
 the same as the normal binary operations.
 
-For targets which are attribute references, the initial value is retrieved with
+If the target is an attribute reference, the initial value is retrieved with
 a :meth:`getattr` and the result is assigned with a :meth:`setattr`.  Notice
 that the two methods do not necessarily refer to the same variable.  When
 :meth:`getattr` refers to a class variable, :meth:`setattr` still writes to an
@@ -264,7 +285,10 @@
    a = A()
    a.x += 1     # writes a.x as 4 leaving A.x as 3
 
+See section :ref:`assignment` for a similar note on
+attribute references.
 
+
 .. _assert:
 
 The :keyword:`assert` statement