How to keep mypy happy using `pydantic.DirectoryPath` with a default value

[michaeloliverx]

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Question

Output of python -c "import pydantic.utils; print(pydantic.utils.version_info())":

             pydantic version: 1.7.2
            pydantic compiled: True
                 install path: /Users/michaeloliver/echo/app/.venv/lib/python3.9/site-packages/pydantic
               python version: 3.9.0 (default, Oct 27 2020, 14:15:17)  [Clang 12.0.0 (clang-1200.0.32.21)]
                     platform: macOS-10.16-x86_64-i386-64bit
     optional deps. installed: ['typing-extensions']

I would like to use DirectoryPath with a default value if no environment override exists (using BaseSettings)

from pathlib import Path

from pydantic import BaseSettings, DirectoryPath

BASE_DIR = Path(__file__).parent


class Config(BaseSettings):
    CONTENT_DIR: DirectoryPath = BASE_DIR / "content"

mypy complains:

src/hublib/config.py:8: error: Incompatible types in assignment (expression has type "Path", variable has type "DirectoryPath")

What would be the best approach ?

[PrettyWood]

Hello @michael0liver thanks for reporting

There are three main ways

• handle it in your code thanks to a # type: ignore or better with a if TYPE_CHECKING condition
• handle the custom types directly in pydantic code
• handle the custom types in pydantic mypy plugin

I just opened a PR with the second solution. You can add this directly in your code

from pathlib import Path
from typing import TYPE_CHECKING

from pydantic import BaseSettings

if TYPE_CHECKING:
    from typing import Union
    DirectoryPath = Union[str, Path]
else:
    from pydantic import DirectoryPath

or add a # type: ignore in the meantime

class Config(BaseSettings):
    CONTENT_DIR: DirectoryPath = BASE_DIR / "content"  # type: ignore

Hope it helps!

[michaeloliverx]

@PrettyWood Thanks for the response 😄