Pydantic: Freezing an instance workaround

pydantic_freezing_instance_workaround.py

from pydantic import BaseModel
from typing import Any

class UnfrozenThing(BaseModel):
    model_config = {"extra": "allow", "validate_assignment": True}
    f: str | None = None
    
    def model_post_init(self, __context: Any) -> None:
        self.f = 'a'
        self.model_config

class FrozenThing(UnfrozenThing):
    model_config = {"extra":"ignore", "validate_assignment": True, "frozen": True}

    def model_post_init(self, __context: Any) -> None:
        pass 

t = FrozenThing.model_validate(UnfrozenThing(f="some string",extra_val=3).model_dump())
t.model_dump()