Python Programming

In our previous code, a problem is that a user can still create a new instance of the Device class via device = Device(). The NotImplementedError exception is only raised when device.turn_off() is invoked.

Perhaps a better way is to not allow instances of Device() to be created in the first place!

To do this, you explicitly turn Device into an abstract class, by subclassing from abc.ABC (Abstract Base Class).

You will also explicitly mark turn_off() as an abstract method using the @abstractmethod decorator. We will talk about decorators in more detail in a future lesson. There is no need to raise a NotImplementedError as before either. A simple pass statement is sufficient.

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from abc import ABC, abstractmethod

class Device(ABC):
    def __init__(self, name):
        self.name = name

    @abstractmethod
    def turn_off(self):
        pass

device = Device("Some device")