Tweak and accept PEP 352 -- new exception hierarchy.

pep-0000.txt

@@ -68,6 +68,7 @@ Index by Category
  SA  308  Conditional Expressions                      GvR, Hettinger
  SA  328  Imports: Multi-Line and Absolute/Relative    Aahz
  SA  343  The "with" Statement                         GvR, Coghlan
+ SA  352  Required Superclass for Exceptions           GvR, Cannon
 
  Open PEPs (under consideration)
 
@@ -105,7 +106,6 @@ Index by Category
  S   345  Metadata for Python Software Packages 1.2    Jones
  I   350  Codetags                                     Elliott
  S   351  The freeze protocol                          Warsaw
- S   352  Required Superclass for Exceptions           GvR, Cannon
  S   353  Using ssize_t as the index type              von Loewis
  S   354  Enumerations in Python                       Finney
  S   355  Path - Object oriented filesystem paths      Lindqvist
@@ -404,7 +404,7 @@ Numerical Index
  SD  349  Allow str() to return unicode strings        Schemenauer
  I   350  Codetags                                     Elliott
  S   351  The freeze protocol                          Warsaw
- S   352  Required Superclass for Exceptions           GvR, Cannon
+ SA  352  Required Superclass for Exceptions           GvR, Cannon
  S   353  Using ssize_t as the index type              von Loewis
  S   354  Enumerations in Python                       Finney
  S   355  Path - Object oriented filesystem paths      Lindqvist

pep-0352.txt

@@ -3,7 +3,7 @@ Title: Required Superclass for Exceptions
 Version: $Revision$
 Last-Modified: $Date$
 Author: Brett Cannon <brett@python.org>, Guido van Rossum <guido@python.org>
-Status: Draft
+Status: Accepted
 Type: Standards Track
 Content-Type: text/x-rst
 Created: 27-Oct-2005
@@ -34,12 +34,15 @@ Introducing a new superclass for exceptions also gives us the chance
 to rearrange the exception hierarchy slightly for the better.  As it
 currently stands, all exceptions in the built-in namespace inherit
 from Exception.  This is a problem since this includes two exceptions
-(KeyboardInterrupt and SystemExit) that are usually meant to signal
-that the interpreter should be shut down.  Changing it so that these
-two exceptions inherit from the common superclass instead of Exception
-will make it easy for people to write ``except`` clauses that are not
-overreaching and not catch exceptions that should propagate up and
-terminate the interpreter.
+(KeyboardInterrupt and SystemExit) that often need to be excepted from
+the application's exception handling: the default behavior of shutting
+the interpreter down with resp. without a traceback is usually more
+desirable than whatever the application might do (with the possible
+exception of applications that emulate Python's interactive command
+loop with ``>>>`` prompt).  Changing it so that these two exceptions
+inherit from the common superclass instead of Exception will make it
+easy for people to write ``except`` clauses that are not overreaching
+and not catch exceptions that should propagate up.
 
 This PEP is based on previous work done for PEP 348 [#pep348]_.
 
@@ -81,9 +84,13 @@ will cause the deprecation of the existing ``args`` attribute)::
                          else self.args)
 
       def __repr__(self):
-          if (len(self.args) <= 1):
-              return "%s(%r)" % (self.__class__.__name__, self.message)
-          return "%s%r" % (self.__class__.__name__, self.args)
+          if not self.args:
+              argss = "()"
+          elif len(self.args) <= 1:
+              argss = "(%s)" % repr(self.message)
+          else:
+              argss = repr(self.args)
+          return self.__class__.__name__ + argss
 
       def __getitem__(self, index):
           """Index into arguments passed in during instantiation.
@@ -201,12 +208,12 @@ desired.
 
 * Python 2.5
 
+  - allow exceptions to be new-style classes
+
+  - all standard exceptions become new-style classes
+
   - introduce BaseException
 
-    + allow exceptions to be new-style classes
-
-    + all standard exceptions become new-style classes
-
   - Exception, KeyboardInterrupt, and SystemExit inherit from BaseException
 
   - deprecate raising string exceptions
@@ -229,7 +236,13 @@ desired.
 
 * Python 3.0
 
-  - drop ``args`` and ``__getitem__``
+  - drop everything that was deprecated above:
+
+    + drop string exceptions (could do this sooner?)
+
+    + all exceptions must inherit from BaseException
+
+    + drop ``args`` and ``__getitem__``
 
 
 Implementation