Issue #13557: Clarify effect of giving two different namespaces to exec or
execfile().
diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst
index 54baecf..a324e51 100644
--- a/Doc/library/functions.rst
+++ b/Doc/library/functions.rst
@@ -430,7 +430,10 @@
The arguments are a file name and two optional dictionaries. The file is parsed
and evaluated as a sequence of Python statements (similarly to a module) using
the *globals* and *locals* dictionaries as global and local namespace. If
- provided, *locals* can be any mapping object.
+ provided, *locals* can be any mapping object. Remember that at module level,
+ globals and locals are the same dictionary. If two separate objects are
+ passed as *globals* and *locals*, the code will be executed as if it were
+ embedded in a class definition.
.. versionchanged:: 2.4
formerly *locals* was required to be a dictionary.