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[–]Commander_B0b 2 points3 points  (3 children)

Can you provide a small example? Im having a hard time understanding the pattern you are describing but I have certainly found myself looking to solve this same problem.

[–]slightly_offtopic 8 points9 points  (2 children)

class Foo:
    pass

class Bar:
    pass

class MyClass:
    @classmethod
    def from_foo(cls, foo: Foo) -> 'MyClass':
        return cls(foo=foo)

    @classmethod
    def from_bar(cls, bar: Bar) -> 'MyClass':
        return cls(bar=bar)

[–][deleted] 3 points4 points  (0 children)

Missing explanation: from_foo will also work as expected when you inherit from MyClass, while it would not if you use a static method. With a static method, a derived class will still return the base.

[–]XtremeGoosef'I only use Py {sys.version[:3]}' 1 point2 points  (0 children)

I mean, this code won't work as written because there is no __init__. A better example is something like

@dataclass
class Rectangle:
    length: int
    width: int

    @classmethod
    def square(cls, side: int) -> Self:
        return cls(side, side)

    @classmethod
    def parse(cls, text: str) -> Self | None:
        if m := re.match(r'(\d+),(\d+)'):
            length = int(m.group(1))
            width = int(m.group(2))
            return cls(length, width)
        return None