New submission from David Seddon:
The documentation for functools.total_ordering states that rich comparison can
be enabled on a class by specifying an __eq__ method, and one of __lt__(),
__le__(), __gt__(), or __ge__(). If these instructions are followed, this
results in an incorrect evaluation of the not equal operator:
Here's an example:
from functools import total_ordering
@total_ordering
class Value(object):
def __init__(self, value):
self.value = value
def __eq__(self, other):
return self.value == other.value
def __lt__(self, other):
return self.value < other.value
>>> a = Value(3)
>>> b = Value(3)
>>> a == b
True
>>> a != b
True
I've tested this on 2.7.10.
Either the documentation or the behaviour should be corrected.
https://docs.python.org/2/library/functools.html#functools.total_ordering
----------
messages: 255339
nosy: David Seddon
priority: normal
severity: normal
status: open
title: functools.total_ordering does not correctly implement not equal behaviour
type: behavior
versions: Python 2.7
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue25732>
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