1_classic.py

# interesting but not practical :)
from abc import ABC


class Switch:
    def __init__(self):
        self.state = OffState()

    def on(self):
        self.state.on(self)

    def off(self):
        self.state.off(self)


class State(ABC):
    def on(self, switch):
        print('Light is already on')

    def off(self, switch):
        print('Light is already off')


class OnState(State):
    def __init__(self):
        print('Light turned on')

    def off(self, switch):
        print('Turning light off...')
        switch.state = OffState()


class OffState(State):
    def __init__(self):
        print('Light turned off')

    def on(self, switch):
        print('Turning light on...')
        switch.state = OnState()


if __name__ == '__main__':
    sw = Switch()

    sw.on()  # Turning light on...
             # Light turned on

    sw.off()  # Turning light off...
              # Light turned off

    sw.off()  # Light is already off