Re: [Python-Dev] Why doesn't `functools.total_ordering` use the existing ordering methods?
On Mon, Apr 25, 2011 at 20:43, cool-RR wrote: > Hello, > Today I was trying to use `total_ordering` for the first time. I was > expecting that in order to implement e.g. `x > y` it would do `not x < y and > not x == y`, assuming that `__lt__` and `__eq__` are defined. But I see it > just does `y < x`, which is problematic. For example if you have a class > that is decorated by `total_ordering`, and implements only `__lt__` and > `__eq__`, then trying to do `x < y` will result in infinite recursion. > Why not have `total_ordering` work in the way I suggested? This has been partly fixed for Python 3.2, although it can still happen if you compare two types that both use the total_ordering decorator. See http://bugs.python.org/issue10042 . -- Lennart Regebro: http://regebro.wordpress.com/ Porting to Python 3: http://python3porting.com/ ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Why doesn't `functools.total_ordering` use the existing ordering methods?
On Apr 25, 2011, at 11:43 AM, cool-RR wrote:
> Today I was trying to use `total_ordering` for the first time. I was
> expecting that in order to implement e.g. `x > y` it would do `not x < y and
> not x == y`, assuming that `__lt__` and `__eq__` are defined.
This was fixed. The current code has:
convert = {
'__lt__': [('__gt__', lambda self, other: not (self < other or self ==
other)),
('__le__', lambda self, other: self < other or self ==
other),
('__ge__', lambda self, other: not self < other)],
'__le__': [('__ge__', lambda self, other: not self <= other or self ==
other),
('__lt__', lambda self, other: self <= other and not self ==
other),
('__gt__', lambda self, other: not self <= other)],
'__gt__': [('__lt__', lambda self, other: not (self > other or self ==
other)),
('__ge__', lambda self, other: self > other or self ==
other),
('__le__', lambda self, other: not self > other)],
'__ge__': [('__le__', lambda self, other: (not self >= other) or self
== other),
('__gt__', lambda self, other: self >= other and not self ==
other),
('__lt__', lambda self, other: not self >= other)]
}
> Why not have `total_ordering` work in the way I suggested?
To avoid needless posts, you should use the tracker.
Raymond
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[Python-Dev] Why doesn't `functools.total_ordering` use the existing ordering methods?
Hello, Today I was trying to use `total_ordering` for the first time. I was expecting that in order to implement e.g. `x > y` it would do `not x < y and not x == y`, assuming that `__lt__` and `__eq__` are defined. But I see it just does `y < x`, which is problematic. For example if you have a class that is decorated by `total_ordering`, and implements only `__lt__` and `__eq__`, then trying to do `x < y` will result in infinite recursion. Why not have `total_ordering` work in the way I suggested? Ram. ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
