Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!feeder.erje.net!eu.feeder.erje.net!newsfeed.freenet.ag!news2.euro.net!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail
MIME-Version: 1.0
Date: Mon, 13 May 2013 05:23:16 +0600
Subject: Differences of "!=" operator behavior in python3 and python2 [ bug? ]
From: "Mr. Joe" <titanix88@gmail.com>
To: python-list <python-list@python.org>
Content-Type: text/plain; charset=UTF-8
Precedence: list
Newsgroups: comp.lang.python
Message-ID: <mailman.1603.1368401007.3114.python-list@python.org>
Lines: 40
NNTP-Posting-Host: 2001:888:2000:d::a6
Xref: csiph.com comp.lang.python:45210

I seem to stumble upon a situation where "!=" operator misbehaves in
python2.x. Not sure if it's my misunderstanding or a bug in python
implementation. Here's a demo code to reproduce the behavior -
"""
# -*- coding: utf-8 -*-
from __future__ import unicode_literals, print_function

class DemoClass(object):
    def __init__(self, val):
        self.val = val

    def __eq__(self, other):
        return self.val == other.val

x = DemoClass('a')
y = DemoClass('a')

print("x == y: {0}".format(x == y))
print("x != y: {0}".format(x != y))
print("not x == y: {0}".format(not x == y))
"""

In python3, the output is as expected:
"""
x == y: True
x != y: False
not x == y: False
"""

In python2.7.3, the output is:
"""
x == y: True
x != y: True
not x == y: False
"""
Which is not correct!!

Thanks in advance for clarifications.
Regards,
TB