Inherited class not recognized

Python Help
1

Hello, I have an issue where an inherited class is not recognized by PyLance in VSCode or mypy.

  • OS: Windows 11
  • Python: 3.10.15
  • IDE: VSCode

I have a toolkit\virtualbus.py file containing the following classes:

from toolkit.log import Loggable
from abc import ABCMeta
from typing import final, TYPE_CHECKING
if TYPE_CHECKING:
    from typing import Type

__all__ = ["VirtualBus", "ModuleVirtualBus"]

class VirtualBus(Loggable, metaclass=ABCMeta):
    ... # no abstract methods, only inheriting from ABCMeta

@final
class ModuleVirtualBus(VirtualBus):
    def __new__(cls: "Type[ModuleVirtualBus]") -> "ModuleVirtualBus":
        # singleton pattern
        if cls._instance is None:
            cls._instance = object.__new__(cls)
        return cls._instance

Now I use this toolkit in another package, core. Whenever I try to import ModuleVirtualBus though, via the following:

from toolkit.virtualbus import ModuleVirtualBus

I get the following PyLance error:

"ModuleVirtualBus" is unknown import symbol

And the following mypy error:

Module "toolkit.virtualbus" has no attribute "ModuleVirtualBus"; maybe "VirtualBus"?

In a previous thread, it was pointed out to me that I was supposed to notify mypy of type checking by adding the py.typed file in the source folder of my toolkit package - which I did. Now, I don’t really understand what the issue is in this case. Am I doing something wrong in the inheritance or in exposing the classes?

I’m not doing the imports in toolkit\__init__.py because I want users to import these classes via accessing the virtualbus module, so it’s an intended choice.

Thanks in advance for any help.

2

Apparently, when installing in editable mode, ModuleVirtualBus is correctly recognized.

I should probably mention that I’m installing the toolkit locally, i.e.

pip install path/to/toolkit

But I don’t understand what causes this different behavior wether I’m installing in editable mode or not.

3

The py.typed file is probably not getting copied over. You need to declare it as a datafile for your build backend.

1 Like
4

Thanks for the reply.

Currently the pyproject.toml looks like this (I’m using setuptools as build backend):

[tool.setuptools]
package-dir = {"" = "src"}

[tool.setuptools.packages.find]
where = ["src"]

[tool.setuptools.package-data]
"*" = ["*.typed"]

py.typed is declared in src\toolkit\py.typed, so this should work but still doesn’t. I guess I have to investigate a little more.