How to do python typing for list of classes.
Suppose I have following classes.
from dataclasses import dataclass
@dataclass
class A:
name: str
@dataclass
class B:
age: int
#...
CLASSES = [A, B] #... more classes in list
Now I define a function that instantiate any one of the following class
def func(resource: Union[*CLASSES], value: Union[str, int]):
return resource(value)
But type-hinting is not valid here. How to do type hinting from List?
This achieves what you want using a super-class that all the intended classes share:
from typing import Union
from dataclasses import dataclass
@dataclass
class MyDataMixin:
pass
@dataclass
class A(MyDataMixin):
name: str
@dataclass
class B(MyDataMixin):
age: int
def func(resource: MyDataMixin, value: Union[str, int]):
return resource
You can't use expansion in the type definition of the parameter like you were trying to do, that only works on variables at runtime.
As @Selcuk indicated in the comments, naming it MyDataMixin makes more sense, as the class is not intended to be used by itself. You could go further and ensure it's just an abstract class - but that's beyond the scope of the question.
Mixin so that other (actual) superclasses can be extended if needed.
ABC unless you have specific reasons to want to use an abstract base class, like requiring an abstract method to be implemented on each subclass - but that goes way beyond what you were asking. Just inheriting from a shared base class is enough. Everything else is a different matter.
Union; you can use what @Grismar suggested in their answer. Unions are only necessary if you are using built-in or third party classes that you can't modify.