gh-137658: Fix dataclass order method behaviors to align with the equality semantics #137497
Conversation
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Don't use a PR number as the issue prefix, things get confused. Please can you create an issue for this PR, and add a NEWS entry? Please can you use a A |
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We need to be very careful that we're not changing semantics with this. We've had that problem before with comparisons (although of course now I can't find the issue). I don't think we added tests for this, because we didn't find the problem until after we'd released the code. |
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@ericvsmith so we need set of tests that pass prior to this change? Potentially relevant "semantics" you mention may be shown in the tests for this change in #582? |
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I'm specifically thinking of #128294. We don't want to do something like that again. I haven't looked at this change closely, I just want to be extra careful. |
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@ericvsmith Thanks for that info, I looked into the situation a bit and it seems that since the behavior of 3.13 for I will file an issue for this @dataclasses.dataclass(order=True, slots=True)
class Data:
a: float
class Obj:
__slots__ = "a",
def __init__(self, a: float):
self.a = a
def __eq__(self, other):
if self is other:
return True
if self.__class__ is other.__class__:
return (
self.a == other.a
)
return NotImplemented
def __lt__(self, other):
if self.__class__ is other.__class__:
return self.a < other.a
return NotImplemented
def __le__(self, other):
if self.__class__ is other.__class__:
return self.a <= other.a
return NotImplemented
def __gt__(self, other):
if self.__class__ is other.__class__:
return self.a > other.a
return NotImplemented
def __ge__(self, other):
if self.__class__ is other.__class__:
return self.a >= other.a
return NotImplemented
nan = float("nan")
assert not (Data(nan) < Data(nan))
# assert not (Data(nan) <= Data(nan)), "fails on 3.13 even though {<, ==} are both False"
assert not (Data(nan) > Data(nan))
# assert not (Data(nan) >= Data(nan)), "fails on 3.13 even though {>, ==} are both False"
assert (Data(nan) != Data(nan))
assert not (Data(nan) == Data(nan))
assert not (Obj(nan) < Obj(nan))
assert not (Obj(nan) <= Obj(nan))
assert not (Obj(nan) > Obj(nan))
assert not (Obj(nan) >= Obj(nan))
assert (Obj(nan) != Obj(nan))
assert not (Obj(nan) == Obj(nan)) |
Similar to #104904
This can speed up ordering/comparison operations by ~2x by making the comparison similar to existing
__eq__performance.Benchmark timings for classes with 5 integer fields: