car.py

class Car:
    count = 0       #Car.count 쓰면 안됨

    def __init__(self,type,speed):
        self.type=type
        self.speed=speed
        Car.count +=1           #count만 쓰면 안됨

    @classmethod                #반드시 있어야함
    def get_count(cls):         #꼭 이름이 cls가 아니어도 됨
        return cls.count        #Car.count 써도 됨

    def move(self):
        print(self.type+"가 "+str(self.speed)+" 속도로 움직입니다.")

    def speed_up(self,amount):  #그냥 speed 쓰면 안 됨
        self.speed+=amount

    def speed_down(self,amount):
        self.speed-=amount

print(Car.get_count())

c = Car("스포츠카",200)
c.speed_up(10)
c.move()
c.speed_down(10)
c.move()

d = Car("테슬라",200)
d.speed_up(50)
d.move()
d.speed_down(150)
d.move()

print(Car.get_count())