Rust has a way to implement families of classes without subclassing,
which I think could be a great addition to Python someday.  I'll explain below.

Here is a Rust example (https://youtu.be/WDkv2cKOxx0?t=3795)
that demonstrates a way to implement classes without subclassing.
   
# Rust Code
enum Shape {
    Circle(f32),
    Square(f32),
    Rectangle(f32, f32)
}

impl Shape {
    fn area(self) -> f32 {
        match self {
            Shape::Circle(r) => 3.1 * r * r,
            Shape::Square(l) => l * l,
            Shape::Rectangle(l, w) => l * w
        }
    }
}

fn main () {
    let c = Shape::Circle(3.0);
    let s = Shape::Square(3.0);
    let r = Shape::Rectangle(3.0, 7.5);
    println!("○ {}", c.area());
    println!("□ {}", s.area());
    println!("▭ {}", r.area());
}

# Output
○ 27.899998
□ 9
▭ 22.5

The general idea is:
- declare classes that share a certain type
- extend common methods with a match-case style

That's it.  No sub-classing required.  

I wondered if someday, can we do this in Python? This match-case proposal seems to fit well in this example.

While I know this PEP does not focus on detailed applications,
does anyone believe we can achieve elegant class creation (sans subclassing) with match-cases?