🔒 Set type hinting in IDE when an object is loaded from a unknown function?

[hearty charm]

I have some generic code for loading config in different projects, and part of that monkey patches a class with a load() class function. The problem is that the IDE doesn't see that connection and will always tag the variable as "Any" - even with type hinting on the variable.

CONF: Config = Config.load()

With that, since load() is unknown, the type of CONF will always be "any", and autocomplete suggestions will always be empty. Is there a way to tell the typing system / IDE that "This IS an instance of this class, really"?

I'm using VS Code with Python plugins for IDE

[wispy patio]

@hearty charm

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[signal coral]

usually I do

CONF = Config.load()
CONF: Config
```and it works fine

[hearty charm]

Hm.. Not here, it still identifies it as Any. Which IDE do you use?

[eager solar]

Where is Config defined? Is it in a separate package?

[hearty charm]

It uses this package: https://github.com/TheTerrasque/python-configclass
let me set up a toy example

# pip install git+https://github.com/TheTerrasque/python-configclass
from configclass import configclass

@configclass()
class ExampleConfig:
    setting1: int
    setting2: str

CONF: ExampleConfig = ExampleConfig.load()

[signal coral]

vscode as well

[hearty charm]

If I could fix the configclass code to give right return value that would be the best, but last I looked into it it was ... complicated.. to say the least

[eager solar]

Can you try doing reveal_type(Config)? It’ll produce an error, but also list what type Pyright thinks the class is.

[hearty charm]

https://github.com/TheTerrasque/python-configclass/blob/main/src/configclass/config_class.py#L96 is the class monkeypatching code

[hearty charm]

It's fine at runtime, this is about typing in the ide when writing code.

[eager solar]

reveal_type is a special function type checkers understand.

[hearty charm]

aah, cool.

[eager solar]

Okay so this is probably an issue with it following the import, not with the specific load line.

[eager solar]

What about reveal_type(ExampleConfig), or reveal_type(configclass)?

You may need to go add type hints to your package to get this to work right. In particular, decorate configclass with typing.dataclass_transform(), which tells type checkers to treat your function like @dataclass.

[hearty charm]

Getting that to work would be great, I tried a bit earlier but gave up. Let me try adding that and see.

[eager solar]

The other thing is to instead of making load a method on the class, instead just have it as a function in your module that gets passed in the class. Then you could define it like so:

def load[ClassT](cls: type[ClassT], data: dict | None = None) -> ClassT:
    ...

[hearty charm]

is there a way to tell typing the dataclass will have an attached function that returns an instance of the class?

[eager solar]

Not currently, that'd need an intersection feature in typing.

[hearty charm]

ok

[eager solar]

It's part of the reason why dataclasses doesn't add methods itself, instead using functions. Also this way you can define an option named load.

[hearty charm]

I'll make a load function following your suggestion, thanks. Too bad, I really liked the elegance of the class.load() :/

[wispy patio]

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