Exclude some attributes from fields method of dataclass

Question

I have a python dataclass that looks something like:

@dataclass
class MyDataClass:
    field0: int = 0
    field1: int = 0

    # --- Some other attribute that shouldn't be considered as _fields_ of the class
    attr0: int = 0
    attr1: int = 0

I'd like to write the class in such a way that, when calling dataclasses.fields(my_data:=MyDataClass()), only field0 and field1 are reported.

As a workaround, I've splitted the class in two inheriting classes, as:

@dataclass
class MyData:
    field0: int = 0
    field1: int = 0

class MyDataClass(MyData):
    # --- Some other attribute that shouldn't be considered as _fields_ of the class
    attr0: int = 0
    attr1: int = 0

It works, but I don't know if it's the right way (some drawback I'm not considering?) or if there is a more straightforward way to do it

Answer 1

Not the most elegant solution, but you may declare the non-field attributes as InitVar[int] and set them in a __post_init__() method.

@dataclass
class MyDataClass:
    field0: int = 0
    field1: int = 0

    # --- Some other attribute that shouldn't be considered as _fields_ of the class
    attr0: InitVar[int] = 0
    attr1: InitVar[int] = 0
    
    def __post_init__(self, attr0, attr1):
        self.attr0 = attr0
        self.attr1 = attr1