在Python数据类中创建唯一的ID

我的 python 数据类需要一个唯一的（无符号整数）id。这是非常相似 to 这个帖子 https://stackoverflow.com/questions/58101476/how-to-create-a-unique-and-incremental-id-in-a-python-class, but without明确的演员。

import attr
from attrs import field
from itertools import count
@attr.s(auto_attribs=True)
class Person:
    #: each Person has a unique id
    _counter: count[int] = field(init=False, default=count())
    _unique_id: int = field(init=False)

    @_unique_id.default
    def _initialize_unique_id(self) -> int:
        return next(self._counter)

还有更多“pythonic”解决方案吗？

Use a default factory instead of just a default. https://docs.python.org/3/library/dataclasses.html#default-factory-functions This allows to define a call to get the next id on each instantiation.
A simple means to get a callable that counts up is to use count().__next__, the equivalent of calling next(...) on a count instance.¹

常见的“无显式构造函数”库attr and dataclasses两者都支持这一点：

from itertools import count
from dataclasses import dataclass, field

@dataclass
class C:
    identifier: int = field(default_factory=count().__next__)

import attr

@attr.s
class C:
    identifier: int = attr.field(factory=count().__next__)

要始终使用自动生成的值并防止将其作为参数传递，请使用init=False.

@dataclass
class C:
    identifier: int = field(default_factory=count().__next__, init=False)

¹ If one wants to avoid explicitly addressing magic methods, one can use a closure over a count. For example, factory=lambda counter=count(): next(counter).