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

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Bugs item #847024, was opened at 2003-11-22 02:39
Message generated for change (Comment added) made by gbrandl
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Category: Type/class unification
Group: Python 2.3
>Status: Closed
>Resolution: Fixed
Priority: 5
Submitted By: Michael Dubner (dubnerm)
Assigned to: Michael Hudson (mwh)
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


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>Comment By: Georg Brandl (gbrandl)
Date: 2006-02-20 19:53

Message:
Logged In: YES 
user_id=849994

This now seems to be fixed in 2.5 HEAD and 2.4 branch. Cheers!

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

Comment By: Georg Brandl (birkenfeld)
Date: 2005-10-01 13:38

Message:
Logged In: YES 
user_id=1188172

I could reproduce with all my Pythons. I looked around a bit
but couldn't find any cause of this. Michael, do you have
more luck?

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