car.py

class Car:
    acceleration = 2
    braking = 3
    desired_speed = 30 # mps = 108 km/hr
    minimum_spacing = 15
    slowing_prob = 0.2

    def __init__(self, speed=0, location=0):
        self.speed = speed
        self.location = location

    def speed_kmh(self):
        return int(self.speed / KMH_TO_MPS)

    def accident_chance(self):
        return BASE_FATALITY_CHANCE_PER_KM * (1.03 ** self.speed_kmh())

    def next_probable_location(self):
        return self.location + self.speed

    def move(self, other_cars):
        """Returns a new Car with a new location and speed_mps. Does this
        so that we can loop over all cars to get their next speed and location
        without mutating them, preventing issues with some cars moved with others
        not yet moving."""

        def distance(car):
            return car.next_probable_location() - self.next_probable_location()

        def too_close(distance):
            return 0 < distance < self.minimum_spacing

        speed = self.speed
        location = self.location

        if self.speed < self.desired_speed:
            speed += self.acceleration

        distances = [distance(car) for car in other_cars]
        cars_too_close = [too_close(d) for d in distances]
        if any(cars_too_close):
            speed = min(d for d in distances if d > 0)

        if random.random() < self.slowing_prob:
            speed -= self.braking
            
        speed = speed if speed > 0 else 0

        location += speed

        return Car(speed, location)
    
    def __repr__(self):
        return "<Car speed={} location={}>".format(self.speed, self.location)