CODEWITHSUNDEEP
pythondjangopycharmpython-typing
Ivan Trushin
Ivan Trushin

Reputation: 358

Type hinting for Django Model subclass

I have helper function for Django views that looks like this (code below). It returns None or single object that matches given query (e.g. pk=1).

from typing import Type, Optional

from django.db.models import Model

def get_or_none(cls: Type[Model], **kwargs) -> Optinal[Model]:
    try:
        return cls.objects.get(**kwargs)
    except cls.DoesNotExist:
        return None

Supose I have created my own model (e.g. Car) with its own fields (e.g. brand, model). When I asign results of get_or_none function to a varibale, and then retriveing instance fields, I get annoying warning in PyCharm of unresolved reference.

car1 = get_or_none(Car, pk=1)

if car1 is not None:
    print(car1.brand) # <- Unresolved attribute reference 'brand' for class 'Model'

What's the propper type hinting to get rid of this warning and get code completion for variable)?

Upvotes: 8

Views: 3937

Answers (1)

Ivan Trushin
Ivan Trushin

Reputation: 358

Found this answer to almost simmilar question. The solution is to use TypeVar from typing

from typing import TypeVar, Type, Optional

from django.db.models import Model


T = TypeVar('T', bound=Model)

def get_or_none(cls: Type[T], **kwargs) -> Optional[T]:
    ... # same code

And everything works fine: no warnings and code completion

Upvotes: 7

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