How to store references to objects in pydantic models, not copies

[theRealSuperMario]

Hi,

I make a quick example to illustrate my point:

import pydantic
from dataclasses import dataclass
from pydantic import BaseModel


"""When using BaseModel as base class for Point, changes are not forwarded to Point"""

class Point(BaseModel):
    x: float
    y: float
    z: float

    def __init__(self, x, y, z) -> None:
        super().__init__(x=x, y=y, z=z)


@dataclass
class Line1:
    start: Point
    end: Point


@pydantic.dataclasses.dataclass
class Line2:
    start: Point
    end: Point


start1 = Point(0, 0, 0)
end1 = Point(1, 0, 0)

start2 = Point(0, 0, 0)
end2 = Point(1, 0, 0)



line1 = Line1(start1, end1)
line1.start.x += 1
assert line1.start.x == 1
assert start1.x == 1


line2 = Line2(start2, end2)
line2.start.x += 1
assert line2.start.x == 1
assert start2.x == 1

import pydantic
from dataclasses import dataclass
from pydantic import BaseModel


"""When using dataclass as base class for Point, changes ARE forwarded to Point"""


@pydantic.dataclasses.dataclass
class Point:
    x: float
    y: float
    z: float


@dataclass
class Line1:
    start: Point
    end: Point


@pydantic.dataclasses.dataclass
class Line2:
    start: Point
    end: Point


start1 = Point(0, 0, 0)
end1 = Point(1, 0, 0)

start2 = Point(0, 0, 0)
end2 = Point(1, 0, 0)



line1 = Line1(start1, end1)
line1.start.x += 1
assert line1.start.x == 1
assert start1.x == 1


line2 = Line2(start2, end2)
line2.start.x += 1
assert line2.start.x == 1
assert start2.x == 1

I was just wondering:

1. if this nuanced difference in behaviour is intentional, and where I could find this in the doc
2. How can I make a BaseModel behave like the data class (i.e. make code block 1 run).

Thanks guys. Cheers  🍺

[PrettyWood]

Hi @theRealSuperMario
Have you checked Config.copy_on_model_validation ? :)

class Point(BaseModel):
    x: float
    y: float
    z: float

    def __init__(self, x, y, z) -> None:
        super().__init__(x=x, y=y, z=z)

    class Config:
        copy_on_model_validation = False

Hope it helps!

[theRealSuperMario]

Not yet. I will check it out.

[theRealSuperMario]

does the trick. Thx