Let me put this another way. In your code example, you let the definition of car directly follow the class definition. I mean the line car = Car().
If you copy-paste or enter it like that in the REPL, it won’t work. You need to keep hitting enter after the class definition (effectively two times) until you get a new prompt (the >>>). So if I do this on my pc, it looks like this:
Python 3.8.5 (default, Jul 28 2020, 12:59:40)
[GCC 9.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> class Car:
... speed = 0
... started = False
...
... def start(self):
... self.started = True
... print("Car started, let's ride!")
...
... def increase_speed(self, delta):
... if self.started:
... self.speed = self.speed + delta
... print('Vrooooom!')
... else:
... print("You need to start the car first")
...
... def stop(self):
... self.speed = 0
... print('Halting')
...
>>> car = Car()
>>> car.increase_speed(10)
You need to start the car first
>>>
As mentioned below, I’d suggest staying away from files for now and try to get this working in the REPL first.
Hope that clears it up!