architect_v3.py

from typing import List

class House:
    def __init__(self, rooms: List[Room]):
        self.rooms = rooms
    
    def __len__(self):
        return len(self.rooms)
    
    def __getitem__(self, item):
        return self.rooms[item]
    
    def area(self) -> int:
        return sum(room.area() for room in self.rooms)


house = House([])
assert len(house) == 0