from typing import Protocol, runtime_checkable, List
@runtime_checkable # opcional, permite isinstance em runtime
class SupportsArea(Protocol):
def area(self) -> float: ...
class Triangle: # NÃO herda de nada
def __init__(self, b: float, h: float) -> None:
self.b, self.h = b, h
def area(self) -> float:
return 0.5 * self.b * self.h
def paint_needed(shape: SupportsArea, coverage: float) -> float:
return shape.area() / coverage
def batch_paint(shapes: List[SupportsArea], coverage: float) -> float:
return sum(s.area() for s in shapes) / coverage
# mypy aceita Triangle; ele “bate” estruturalmente
tri = Triangle(4, 5)
print(paint_needed(tri, 10))
# runtime check opcional
import inspect, math
assert isinstance(tri, SupportsArea) # True
assert not isinstance(math, SupportsArea) # False
