Automatically mark an attrribute as private

[MVrachev]

Hi, I am wondering why there is the need to explicitly mark certain fields as PrivateAttr when
it's forbidden to use underscore as a prefix for a normal field name:
#1476 (comment)

Can't pydantic automatically mark the attributes starting with an underscore as PrivateAttr without the need of specifically marking them as private?
This way users will easily name their attributes without wondering what names are allowed and when to use PrivateAttr.

[PrettyWood]

Hi @MVrachev
Did you check Config.underscore_attrs_are_private?

from pydantic import BaseModel


class M(BaseModel):
    x: str
    y: int
    _private_x: str
    _private_y: int = 2

    class Config:
        underscore_attrs_are_private = True


m = M(x='q', y=1)
assert not hasattr(m, '_private_x')
m._private_x = 'w'
assert hasattr(m, '_private_x')
assert m._private_x == 'w'
assert m._private_y == 2

Hope it helps!

[MVrachev]

Yes, but this still requires me to create a Config class and use the underscore_attrs_are_private field.
Why do I have to use anything at all?

Why not enable this by default when you can't have a public attribute with a name starting with an underscore?

[samuelcolvin]

To avoid backwards compatibility problem in minor releases.

I guess we could change it in v2. Any reason not to @PrettyWood?

[PrettyWood]

Yep was thinking the same! It would make sense

[MVrachev]

That would be awesome!
It would make it so much easier to interact with private attributes.