Pydantic and Pydantic Settings don't seem to provide library stubs for MyPy

[bmitc]

Initial Checks

• I confirm that I'm using Pydantic V2

Description

In the Pydantic documentation for MyPy, it is stated that:

Pydantic works well with mypy right out of the box.

However, Pydantic also ships with a mypy plugin that adds a number of important pydantic-specific features to mypy that improve its ability to type-check your code.

However, MyPy generates errors for a simple module,

error: Cannot find implementation or library stub for module named "pydantic"  [import-not-found]
note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
error: Cannot find implementation or library stub for module named "pydantic_settings"  [import-not-found]
error: Class cannot subclass "BaseModel" (has type "Any")  [misc]
error: Class cannot subclass "BaseModel" (has type "Any")  [misc]
error: Class cannot subclass "BaseSettings" (has type "Any")  [misc]

I've removed the line numbers because they don't match up anyway to the code example below since I removed documentation lines, but they don't matter anyway since MyPy doesn't typecheck any Pydantic piece.

As a note, I am using Poetry. Here is my pyproject.toml configuration for MyPy:

[tool.mypy]
plugins = ["pydantic.mypy"]
strict = true
follow_imports = "silent"

Whether plugins is present or not makes no difference to the errors above.

Example Code

from typing import Tuple, Type, Set
from pydantic import BaseModel
from pydantic_settings import (
    BaseSettings,
    PydanticBaseSettingsSource,
    SettingsConfigDict,
    YamlConfigSettingsSource,
)

class _DeviceConfig(BaseModel):
    bench: int
    side: Side

class _TCPDeviceConfig(BaseModel):
    ip_address: str
    port: int
    is_enabled: bool

class EmbeddedDeviceConfig(_TCPDeviceConfig, _DeviceConfig): pass

class FrontendDeviceConfig(_TCPDeviceConfig): pass

class TelemetryInfluxDBConfig(_TCPDeviceConfig): pass

class TelemetryGrafanaDBConfig(_TCPDeviceConfig): pass

class Settings(BaseSettings):
    telemetry_influxdb: TelemetryInfluxDBConfig
    telemetry_grafana: TelemetryGrafanaDBConfig
    embedded_devices: Set[EmbeddedDeviceConfig]
    frontend_device: FrontendDeviceConfig

    model_config = SettingsConfigDict(yaml_file="configuration.yaml")

    # pylint: disable=too-many-arguments
    @classmethod
    def settings_customise_sources(
        cls,
        settings_cls: Type[BaseSettings],
        init_settings: PydanticBaseSettingsSource,
        env_settings: PydanticBaseSettingsSource,
        dotenv_settings: PydanticBaseSettingsSource,
        file_secret_settings: PydanticBaseSettingsSource,
    ) -> Tuple[PydanticBaseSettingsSource, ...]:
        return (YamlConfigSettingsSource(settings_cls),)

Python, Pydantic & OS Version

             pydantic version: 2.7.1
        pydantic-core version: 2.18.2
          pydantic-core build: profile=release pgo=true
                 install path: <poetry-project-root>\.venv\Lib\site-packages\pydantic
               python version: 3.12.1 (tags/v3.12.1:2305ca5, Dec  7 2023, 22:03:25) [MSC v.1937 64 bit (AMD64)]
                     platform: Windows-11-10.0.22631-SP0
             related packages: mypy-1.9.0 pydantic-settings-2.2.1 typing_extensions-4.11.0
                       commit: unknown

[Viicos]

There's probably an issue with your venv management: are you sure you are running mypy in the same env you have pydantic and pydantic-settings installed?

[bmitc]

I don't install anything with pip directly and always add dependencies via poetry add <package>. So for this case, I would have done poetry add pydantic-settings. Also, I force Poetry to write the .venv to the local project directory so that it's always using the local .venv and not some .venv somewhere else on the computer. Lastly, I always run MyPy via Poetry, so it's something like poetry run mypy .... I have several dependencies installed, but Pydantic seems to be the only one with this issue.

Is there a listing of files that one would expect in the .venv for Pydantic such that MyPy can work with it?

[sydney-runkle]

Hmm, I'm going to move this to a discussion. I think @Viicos is right, this probably relates to venv management.

[bmitc]

How do you know that without any diagnosis or debugging steps? It seems like an assumption because, as I said, the several other packages I am using do not have this problem. So there's a virtual environment problem that only affects Pydantic? Maybe there is, but I need some help knowing what debugging steps the Pydantic team suggests.

[Viicos]

I've tried the following:

mkdir tmp && cd tmp/
poetry init
...

Ending up with the following pyproject.toml:

[tool.poetry]
name = "tmp"
version = "0.1.0"
description = ""
readme = "README.md"

[tool.poetry.dependencies]
python = "^3.10"
pydantic = "^2.7.2"
pydantic-settings = "^2.2.1"
mypy = "^1.10.0"


[build-system]
requires = ["poetry-core"]
build-backend = "poetry.core.masonry.api"

[tool.mypy]
plugins = ["pydantic.mypy"]
strict = true
follow_imports = "silent"

Then:

poetry config virtualenvs.in-project true --local
mkdir tmp/
touch tmp/__init__.py  // and added your example file
poetry run mypy tmp/
// No errors

[lwaekfjlk]

I am facing the same issue.

[utopianf]

Same as me. I am working in python 3.11.8-slim docker, with Poetry and Pydantic version is following:

pydantic-settings = "^2.2.1"
pydantic = "^2.7.0"
mypy = "^1.8.0"

[utopianf]

This was due to my failure settings on pre-commit. I have to add pydantic-settings into the dependancy of mypy