[ python-Bugs-847024 ] NotImplemented return value misinterpreted in new classes

[SourceForge.net]

Bugs item #847024, was opened at 2003-11-22 05:39
Message generated for change (Tracker Item Submitted) made by Item Submitter
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=847024&group_id=5470

Category: Type/class unification
Group: Python 2.3
Status: Open
Resolution: None
Priority: 5
Submitted By: Michael Dubner (dubnerm)
Assigned to: Nobody/Anonymous (nobody)
Summary: NotImplemented return value misinterpreted in new classes

Initial Comment:
Following program:
------------------------------ notimpl.py
class CClassic:
  def __add__(self, other):
    return NotImplemented
  def __mul__(self, other):
    return NotImplemented
class CNew(object):
  def __add__(self, other):
    return NotImplemented
  def __mul__(self, other):
    return NotImplemented

a=CClassic()
try:
  print a+2
except Exception, e:
  print e
try:
  print a*2
except Exception, e:
  print e
a=CNew()
try:
  print a+2
except Exception, e:
  print e
try:
  print a*2
except Exception, e:
  print e
--------------------------------
Output following (correct) under Python 2.2:

unsupported operand types for +: 'instance' and 'int'
unsupported operand type(s) for *: 'instance' and 'int'
unsupported operand types for +: 'CNew' and 'int'
unsupported operand type(s) for *: 'CNew' and 'int'

And following (wrong) under Python 2.3[.2]:

unsupported operand type(s) for +: 'instance' and 'int'
unsupported operand type(s) for *: 'instance' and 'int'
unsupported operand type(s) for +: 'CNew' and 'int'
NotImplemented


----------------------------------------------------------------------

You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=847024&group_id=5470