[Python-checkins] r66834 - peps/trunk/pep-3110.txt

[georg.brandl]

Author: georg.brandl
Date: Tue Oct  7 18:04:41 2008
New Revision: 66834

Log:
Fix w.r.t. exception tuples.


Modified:
   peps/trunk/pep-3110.txt

Modified: peps/trunk/pep-3110.txt
==============================================================================
--- peps/trunk/pep-3110.txt	(original)
+++ peps/trunk/pep-3110.txt	Tue Oct  7 18:04:41 2008
@@ -83,7 +83,7 @@
 
 The use of ``as`` in place of the comma token means that ::
 
-    except AttributeError, os.error:
+    except (AttributeError, os.error):
     
 can be clearly understood as a tuple of exception classes. This new
 syntax was first proposed by Greg Ewing [#firstproposal]_ and
@@ -93,6 +93,14 @@
 to ``NAME`` means that only valid identifiers can be used as
 ``except`` targets.
 
+Note that the grammar above always requires parenthesized tuples as
+exception clases. That way, the ambiguous ::
+
+    except A, B:
+
+which would mean different things in Python 2.x and 3.x -- leading to
+hard-to-catch bugs -- cannot legally occur in 3.x code.
+
 
 Semantic Changes
 ================