Python Dataclasses中自定义方法继承的深度解析与解决方案

import datetime
from dataclasses import dataclass, astuple
from typing import Iterator, Optional

# 定义一个混入类，实现自定义的__eq__和__iter__
class ComparisonMixin:
    def __eq__(self, __o: object) -> bool:
        # 确保比较的是同类型实例
        if not isinstance(__o, type(self)):
            return NotImplemented

        result = True
        # 遍历实例的字段进行比较
        # astuple(self) 需要dataclass支持，这里假设子类是dataclass
        # 实际上，Mixin的__iter__应该基于子类的字段，或者Mixin本身也是dataclass
        # 为了演示问题，我们假设astuple(self)能正常工作
        try:
            for s, o in zip(astuple(self), astuple(__o)):
                if isinstance(s, datetime.datetime) and isinstance(o, datetime.datetime):
                    margin = datetime.timedelta(days=3)
                    result = result and s - margin <= o <= s + margin
                elif o is not None: # 只有当o不是None时才进行精确比较
                    result = result and s == o
                # 如果o是None，而s不是None，则取决于具体业务逻辑，这里默认不影响result
            return result
        except TypeError: # astuple可能因为非dataclass实例而失败
            return NotImplemented

    def __iter__(self) -> Iterator[datetime.datetime | float | str]:
        # 这里的astuple(self)要求self是一个dataclass实例
        return iter(astuple(self))

# 定义一个继承ComparisonMixin的dataclass
@dataclass
class Bloodsample(ComparisonMixin):
    datetime: datetime.datetime
    substance: str
    value: float
    category: Optional[str] = None

# 测试自定义比较逻辑
sample = Bloodsample(datetime.datetime(2024, 1, 9), "hemoglobin", 9.5, "hematology")
sample_with_none_value = Bloodsample(datetime.datetime(2024, 1, 9), "hemoglobin", 9.5, None)

# 预期结果为True，但实际为False，并抛出AssertionError
# assert sample == sample_with_none_value 
# 如果运行此断言，会失败

import datetime
from dataclasses import dataclass, astuple
from typing import Iterator, Optional

# 混入类保持不变
class ComparisonMixin:
    def __eq__(self, __o: object) -> bool:
        if not isinstance(__o, type(self)):
            return NotImplemented

        result = True
        try:
            # 确保astuple能正确获取字段值
            for s, o in zip(astuple(self), astuple(__o)):
                if isinstance(s, datetime.datetime) and isinstance(o, datetime.datetime):
                    margin = datetime.timedelta(days=3)
                    result = result and s - margin <= o <= s + margin
                elif o is not None:
                    result = result and s == o
            return result
        except TypeError:
            return NotImplemented

    def __iter__(self) -> Iterator[datetime.datetime | float | str]:
        return iter(astuple(self))

# 修改Bloodsample，禁用dataclass自动生成__eq__
@dataclass(eq=False) # 关键：禁用__eq__的自动生成
class Bloodsample(ComparisonMixin):
    datetime: datetime.datetime
    substance: str
    value: float
    category: Optional[str] = None

# 再次测试自定义比较逻辑
sample = Bloodsample(datetime.datetime(2024, 1, 9), "hemoglobin", 9.5, "hematology")
sample_with_none_value = Bloodsample(datetime.datetime(2024, 1, 9), "hemoglobin", 9.5, None)

# 此时断言将通过
assert sample == sample_with_none_value
print("自定义比较逻辑已成功应用。")

import dataclasses

class Foo:
    def __eq__(self, other):
        print("在 Foo 的自定义 __eq__ 中执行")
        return True # 总是返回 True 以便观察效果

@dataclasses.dataclass
class Bar(Foo): # 未禁用__eq__自动生成
    x: int
    y: int

@dataclasses.dataclass(eq=False)
class Baz(Foo): # 禁用__eq__自动生成
    x: int
    y: int

print("--- 测试 Bar 类 ---")
# Bar的__eq__由dataclass生成，基于字段比较
# Bar(1,2) == Bar(1,3) 字段y不同，所以返回False
print(Bar(1,2) == Bar(1, 3)) 

print("\n--- 测试 Baz 类 ---")
# Baz的__eq__未由dataclass生成，使用Foo的__eq__
# Foo的__eq__会打印消息并返回True
print(Baz(1,2) == Baz(1, 3))

--- 测试 Bar 类 ---
False

--- 测试 Baz 类 ---
在 Foo 的自定义 __eq__ 中执行
True