214 Creating objects from a class

1. What does the term instantiation mean in object-oriented programming?

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Instantiation is the process of creating an object (or instance) from a class. It involves using the class as a blueprint to create a working object that has its own data and can perform behaviours defined in the class.

1. In the LightSwitch example, what does oLightSwitch = LightSwitch() do?

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This statement creates a new LightSwitch object (an instance of the LightSwitch class) and assigns it to the variable oLightSwitch.

1. Explain the difference between a class and an object using the LightSwitch example.

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The LightSwitch class defines what data (state) and behaviours (methods) a light switch will have. An object, like oLightSwitch, is a specific instance of the class that contains its own data and can perform the behaviours defined by the class.

1. Write a Python line of code that creates a third LightSwitch object called oLightSwitch3.

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oLightSwitch3 = LightSwitch()

1. If oLightSwitch1 and oLightSwitch2 are both instances of LightSwitch, what happens to oLightSwitch2.switchIsOn when you call oLightSwitch1.turnOn()?

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Nothing happens to oLightSwitch2.switchIsOn. Each object has its own copy of switchIsOn, so calling turnOn() on oLightSwitch1 only affects its own switchIsOn value.

1. Look at this code and predict what will be printed:

class LightSwitch():
    def __init__(self):
        self.switchIsOn = False

    def turnOn(self):
        # turn the switch on 
         self.switchIsOn = True

    def turnOff(self):
        # turn the switch off
         self.switchIsOn = False

    def show(self):  # added for testing
        print(self.switchIsOn)
    
# Main code
oLightSwitch1 = LightSwitch()
oLightSwitch2 = LightSwitch()
oLightSwitch1.turnOn()
oLightSwitch1.show()
oLightSwitch2.show()

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The output will be:

True
False

oLightSwitch1 was turned on, so its switchIsOn is True. oLightSwitch2 was not turned on, so its switchIsOn remains False.

1. Write a short code snippet that creates two LightSwitch objects, turns one on, and prints the state of both.

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oLightSwitch1 = LightSwitch()
oLightSwitch2 = LightSwitch()
oLightSwitch1.turnOn()
oLightSwitch1.show()
oLightSwitch2.show()