# compare_test.py
@total_ordering
class StrictComparator(object):
...
def __lt__(self, other):
if not isinstance(other, StrictComparator):
return NotImplemented
else:
return (self.v other.v) - (self.v other.v)
It looks
On Mon, Jan 25, 2010 at 6:59 AM, Lennart Regebro lrege...@jarn.com wrote:
[snip]
If class A returns NotImplemented when compared to class B, and class
B implements the recipe above, then we get infinite recursion, because
1. A() B() will call A.__lt__(B) which will return NotImplemented.
2.
On Tue, Jan 26, 2010 at 09:15, Юлий Тихонов july.t...@gmail.com wrote:
It looks like __cmp__, not __lt__ method.
Oh, yeah, sorry. I copy/pasted code from my code where I use __cmp__, :)
However, with this replacement test also falls into recursion.
Told ya. :)
--
Lennart Regebro: Python,
Lennart Regebro wrote:
It never gets to that root comparison, as several of that types
comparisons just refer back to the type who returns NotImplemented. To
solve it you need to never refer to the other type in your
comparisons. And as far as I see that makes it impossible to implement
full
On 26/01/2010 12:22, Nick Coghlan wrote:
Lennart Regebro wrote:
It never gets to that root comparison, as several of that types
comparisons just refer back to the type who returns NotImplemented. To
solve it you need to never refer to the other type in your
comparisons. And as far as I see
If you look at the description of the rich comparison methods in the
documentation:
http://docs.python.org/reference/datamodel.html#object.__lt__
It refers to a recipe: http://code.activestate.com/recipes/576529/
However, that recipe will convert a __ge__(self, other) into a other self.
So when
Lennart Regebro wrote:
1. A() B() will call A.__lt__(B) which will return NotImplemented.
2. which will mean that Python calls B.__ge__(A)
3. Which B implements by doing A B
4. Start over at 1.
Have I missed something, or is this recipe incomplete by not handling
the NotImplemented
On Mon, Jan 25, 2010 at 14:34, Nick Coghlan ncogh...@gmail.com wrote:
However, returning NotImplemented generally implies that A and B are
*different* classes
Which is exactly the case here.
so I think this is more of a theoretical problem
than a practical one.
How so? The whole point of
Lennart Regebro wrote:
On Mon, Jan 25, 2010 at 14:34, Nick Coghlan ncogh...@gmail.com wrote:
However, returning NotImplemented generally implies that A and B are
*different* classes
Which is exactly the case here.
It wasn't in my tests though - I used the same class on both sides of
the
On Mon, Jan 25, 2010 at 15:30, Nick Coghlan ncogh...@gmail.com wrote:
Ah, you mean the case where both classes implement the recipe, but know
nothing about each other and hence both return NotImplemented from their
root comparison?
Well, only one needs to return NotImplemented, actually.
OK,
Lennart Regebro wrote:
On Mon, Jan 25, 2010 at 15:30, Nick Coghlan ncogh...@gmail.com wrote:
Ah, you mean the case where both classes implement the recipe, but know
nothing about each other and hence both return NotImplemented from their
root comparison?
Well, only one needs to return
On Tue, Jan 26, 2010 at 02:56, Nick Coghlan ncogh...@gmail.com wrote:
Lennart Regebro wrote:
On Mon, Jan 25, 2010 at 15:30, Nick Coghlan ncogh...@gmail.com wrote:
Ah, you mean the case where both classes implement the recipe, but know
nothing about each other and hence both return
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