Hey i was wondering about next behaviour

If we have lets say dataclass with None values by default and we want to re-set a value for future instances of this class, the current behaiour of __post_init__ does not take to the account changed static value and pass to the signature loaded first in memory described values of the class.

@dataclass
class A:
    attr1: str = None
    attr2: str = None

    def __post_init__(self):
        if not A.attr2:
            self.attr2 = '1234'

    def __str__(self):
        return f'{self.attr1} - {self.attr2}'


A.attr2 = 'qwe'
a = A(attr1='oneoneone')
print(a)

At first I expected that all instances of A would have

attr2 = 'qwe'

But it does not, because it loaded with None being passed to __post_init__.

oneoneone - None

If we change default value of attr2 to

@dataclass
class A:
    attr1: str = None
    attr2: str = 'QWERTY'

We see the initializer works

oneoneone - QWERTY