lift.py

import time
import random


def main():
    lift = Lift(10)
    while True:
        lift.move()
        time.sleep(0.3)

        if random.randrange(3) == 1:
            floor = random.randrange(10)
            lift.go_to_floor(floor)
            print("  called to", floor, end="")
        if random.randrange(3) == 1:
            floor, direction = random.randrange(10), random.choice((1, -1))
            lift.call_to_floor(floor, direction)
            print("  called from", floor, "going", direction, end="")
        print()


class Lift:
    def __init__(self, num_floors, initial_floor=0):
        self.floors = [0] * num_floors
        self.current_floor = initial_floor
        self.direction = 1

    def call_to_floor(self, floor, direction):
        if direction not in {1, -1}:
            raise ValueError
        if self.floors[floor] == 4:
            return
        if self.floors[floor] == -direction:
            self.floors[floor] = 4
        else:
            self.floors[floor] = direction

    def go_to_floor(self, floor):
        self.floors[floor] = 4

    def print_info(self):
        floor_vis = (
            str(self.current_floor).rjust(self.current_floor).ljust(len(self.floors))
        )
        print(floor_vis, self.floors, self.direction, end="")

    def move(self):
        self.print_info()
        if any(self.floors):
            if self.floors[self.current_floor] in {4, self.direction}:
                print("  Opened doors", end="")
                self.floors[self.current_floor] = 0
                return
            if self.current_floor == 0:
                self.direction = 1
            for floor in self.floors[
                self.current_floor + self.direction :: self.direction
            ]:
                if floor:
                    self.current_floor += self.direction
                    break
            else:
                self.direction = -self.direction


if __name__ == "__main__":
    main()