Python 数据类从构造函数调用父字段

Question

是否可以继承数据 class 并在子构造函数中使用父字段？

import dataclasses


def get_id():
    return "some unique id"

@dataclasses.dataclass
class Parent:
    name: str
    uid: str = dataclasses.field(default_factory=lambda: get_id())

@dataclasses.dataclass
class Child(Parent):
    dependent_on_id: str = dataclasses.field(default_factory=lambda: f"with {super.uid}")


c = Child(name='x')
print("foo " + c.uid)
print(c.dependent_on_id)

输出：

Traceback (most recent call last):
  File "stack_questions.py", line 17, in <module>
    c = Child(name='x')
  File "<string>", line 5, in __init__
  File "stack_questions.py", line 14, in <lambda>
    dependent_on_id: str = dataclasses.field(default_factory=lambda: f"with {super.uid}")
AttributeError: type object 'super' has no attribute 'uid'

想要输出：

foo some unique id
with foo some unique id

目前在我看来，我最好的解决方案是通过组合而不是继承来实现

Answer 1

super 在这种情况下没有意义。您可以使用数据类的 __post_init__ 方法来设置 dependent_on_id.

@dataclasses.dataclass
class Child(Parent):
    dependent_on_id: str = None 

    def __post_init__(self):
        if not self.dependent_on_id:
            self.dependent_on_id = f"with {self.uid}" # you don't need super

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