validate_assignment=False after model initialization and invoking a setter does not disable assignment validation #11729Description
Initial Checks
- I confirm that I'm using Pydantic V2
Description
I recently switched from pydantic version 2.10.6 to 2.11.3. I have a pydantic model with validate_assignment=True by default. For testing, I temporarily disable this assignment validation to modify a model instance. After the version bump, the code throws a validation error. I have attached a minimal example below. The code works as expected on v2.10.6, but fails with a validation error on v2.11.0, v2.11.1, and v2.11.3.
I suspect that the issue is related to #10868, because it only occurs if a setter is invoked before the assignment validation is disabled. Translated to the example script below, if you remove the lines
# Need to invoke a setter (I suspect to trigger the memoization)
example.list1 = [1, 2, 3]no validation error is thrown.
Please, let me know if the explanation is not clear enough or I can support in any other way.
Thanks a lot for your help and the great tool! :)
Example Code
# /// script
# requires-python = ">=3.10"
# dependencies = [
# "pydantic==2.11.3",
# ]
# ///
import pydantic
from pydantic import BaseModel, ConfigDict, model_validator
class Example(BaseModel):
list1: list[int]
list2: list[str]
model_config = ConfigDict(
validate_assignment=True,
)
@model_validator(mode="after")
def check_list_lengths(self):
if len(self.list1) != len(self.list2):
raise ValueError("list1 and list2 must have the same length")
return self
if __name__ == "__main__":
print(f"Pydantic version: {pydantic.__version__}")
example = Example(list1=[1, 2, 3], list2=["a", "b", "c"])
print(example)
# Need to invoke a setter (I suspect to trigger the memoization)
example.list1 = [1, 2, 3]
print(example)
example.model_config["validate_assignment"] = False
example.list1 = [1, 2]
example.list2 = ["a", "b"]
example.model_config["validate_assignment"] = True
print(example)Python, Pydantic & OS Version
Pydantic version: 2.11.3
pydantic version: 2.11.3
pydantic-core version: 2.33.1
pydantic-core build: profile=release pgo=false
install path: /home/tim/.cache/uv/archive-v0/zd6MbOILWOYXhBpQGNkHW/lib/python3.12/site-packages/pydantic
python version: 3.12.3 (main, Feb 4 2025, 14:48:35) [GCC 13.3.0]
platform: Linux-6.8.0-56-generic-x86_64-with-glibc2.39
related packages: typing_extensions-4.13.1
commit: unknown