How to track mutations in models objects?

[balukrishnans]

Hi,

I need to track the mutations in a model object.
For example

class User(BaseModel):
    id: int
    name: str

user = User(1, "John Doe")
user.name = "John Peter" # Here ∆ = {"name": ("John Doe", "John Peter")}
user.id = 3 # Here ∆ = {"id": (1, 3), "name": ("John Doe", "John Peter")}
user(id = 4, name = "Elton") # Here ∆ = {"id": (3, 4), "name": ("John Peter", "Elton")}

Note: just previous value and current value is need for now

Is there any way to track this in pydantic? Basically, I need a kind of ChainMap like implementation in dataclasses.

[PrettyWood]

Hi @balukrishnans
Something like this

from pydantic import BaseModel


class User(BaseModel, underscore_attrs_are_private = True):
    id: int
    name: str

    _modifs: dict[str, tuple[object, object]] = {}

    def __setattr__(self, key, value):
        old_value = self.__dict__.get(key)
        super().__setattr__(key, value)
        self._modifs[key] = (old_value, value)


user = User(id=1, name="John Doe")
user.name = "John Peter" # Here ∆ = {"name": ("John Doe", "John Peter")}
assert user._modifs == {'name': ('John Doe', 'John Peter')}
user.id = 3 # Here ∆ = {"id": (1, 3), "name": ("John Doe", "John Peter")}
assert user._modifs == {'name': ('John Doe', 'John Peter'), 'id': (1, 3)}

?