attrs

import attr

@attr.s(auto_attribs=True)
class Point:
    x: float
    y: float

    def distance_to(self, other: "Point") -> float:
        return ((self.x - other.x)**2 + (self.y - other.y)**2)**0.5

@attr.s(auto_attribs=True)
class Polygon:
    name: str
    vertices: list = attr.Factory(list)

    def perimeter(self) -> float:
        pts = self.vertices + [self.vertices[0]]
        return sum(pts[i].distance_to(pts[i+1]) for i in range(len(pts)-1))

triangle = Polygon("Triangle", [
    Point(0, 0), Point(4, 0), Point(0, 3)
])

print(repr(triangle))
print(f"Perimeter: {triangle.perimeter():.4f}")
print(f"Expected : 12.0000  (3-4-5 right triangle)")