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gh-137658: Fix dataclass order method behaviors to align with the equality semantics #137497

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gh-137658: Fix dataclass order method behaviors to align with the equality semantics #137497

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94ef589
speedup compare methods
gesslerpd Aug 7, 2025
0827c65
op fix
gesslerpd Aug 7, 2025
1eca2ac
Merge branch 'python:main' into perf-dataclass-order
gesslerpd Aug 7, 2025
b29f17b
add news
gesslerpd Aug 12, 2025
69bf114
add tests
gesslerpd Aug 12, 2025
0432c2a
normalize
gesslerpd Aug 13, 2025
0a98d68
streamline loop (revert if less readable or problematic)
gesslerpd Aug 13, 2025
1eecf2a
add comments
gesslerpd Aug 13, 2025
72027f6
inline now that loop is streamlined
gesslerpd Aug 13, 2025
fa547b5
add "self" comparison checks
gesslerpd Aug 19, 2025
242ae0f
add comments referencing issue to test
gesslerpd Dec 11, 2025
8e10c5b
Merge branch 'main' into perf-dataclass-order
gesslerpd Dec 11, 2025
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speedup compare methods
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@gesslerpd
gesslerpd committed Aug 7, 2025
commit 94ef58993c71edbef209c7a862854870fc16b5ff
23 changes: 17 additions & 6 deletions Lib/dataclasses.py
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Original file line number Diff line number Diff line change
Expand Up @@ -433,6 +433,18 @@ def _tuple_str(obj_name, fields):
return f'({",".join([f"{obj_name}.{f.name}" for f in fields])},)'


def _tuple_compare_expand(op, fields):
if fields:
for f in fields[:-1]:
yield (
f' if self.{f.name} != other.{f.name}:\n'
f' return self.{f.name} {op} other.{f.name}'
)
yield f' return self.{fields[-1].name} {op} other.{fields[-1].name}'
else:
yield ' return True'


class _FuncBuilder:
def __init__(self, globals):
self.names = []
Expand Down Expand Up @@ -1128,21 +1140,20 @@ def _process_class(cls, init, repr, eq, order, unsafe_hash, frozen,
if order:
# Create and set the ordering methods.
flds = [f for f in field_list if f.compare]
self_tuple = _tuple_str('self', flds)
other_tuple = _tuple_str('other', flds)
for name, op in [('__lt__', '<'),
('__le__', '<='),
('__gt__', '>'),
('__ge__', '>='),
]:
# Create a comparison function. If the fields in the object are
# named 'x' and 'y', then self_tuple is the string
# '(self.x,self.y)' and other_tuple is the string
# '(other.x,other.y)'.
# named 'x' and 'y'.
# if self.x != other.x:
# return self.x {op} other.x
# return self.y {op} other.y
func_builder.add_fn(name,
('self', 'other'),
[ ' if other.__class__ is self.__class__:',
f' return {self_tuple}{op}{other_tuple}',
*_tuple_compare_expand(op, flds),
' return NotImplemented'],
overwrite_error='Consider using functools.total_ordering')

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