Lesson 8 · Introduction to Classes — Knowledge ChecksAnswer key

What's the difference between a class and an object?

1. A.They are two words for the same thing
2. B.A class is the blueprint; an object is a specific thing built from it✓
3. C.A class is smaller than an object
4. D.An object is only for sensors

One class (blueprint) can produce many objects (instances). LineSensor is the blueprint; the sensor you create from it is an object.

When does the __init__ method run?

1. A.When you import the file
2. B.When you create an object with LineSensor()✓
3. C.Every time you call any method
4. D.At the end of the program

__init__ is the constructor — Python calls it automatically the moment you build a new object with LineSensor().

You have `sensor = LineSensor()`. How do you call its get_error method?

1. A.sensor.get_error(self)
2. B.sensor.get_error()✓
3. C.get_error(sensor)
4. D.LineSensor.get_error()

You never pass self yourself — Python supplies it automatically. Just sensor.get_error().

Write is_on_line() to return True when AT LEAST ONE sensor is on the line. Which body is correct?

1. A.return self.get_left() > self.threshold or self.get_right() > self.threshold✓
2. B.return self.get_left() > self.threshold and self.get_right() > self.threshold
3. C.return get_left() or get_right()
4. D.return self.threshold

'At least one' means or, and each reading needs self. — self.get_left() > self.threshold or self.get_right() > self.threshold.