relay.py

import gpiozero

# used to track the current state of the relay. At the start, the
# application turns the relay off then sets this variable's value
# the application can then later query this to determine what the
# current state is for the relay, in the toggle function for example.
_relay_status = False

relay = None


def init(relay_pin):
    # initialize the relay object
    print("Initializing relay object")
    global relay
    relay = gpiozero.OutputDevice(relay_pin, active_high=True, initial_value=False)


def status():
    return _relay_status


def set_status(the_status):
    # sets the relay's status based on the boolean value passed to the function
    # a value of True turns the relay on, a value of False turns the relay off
    global _relay_status
    global relay

    if relay is not None:
        _relay_status = the_status

        if the_status:
            print("Setting relay: ON")
            relay.on()
        else:
            print("Setting relay: OFF")
            relay.off()
    else:
        print("You must initialize the relay before you can use it")


def toggle():
    # toggles the relay's status. If the relay is on, when you call this function,
    # it will turn the relay off. If the relay is off, when you call this function,
    # it will turn the relay on. Easy peasy, right?
    global _relay_status
    global relay

    if relay is not None:
        # flip our relay status value
        _relay_status = not _relay_status
        if _relay_status:
            print("Toggling relay: ON")
        else:
            print("Toggling relay: OFF")
        relay.toggle()
    else:
        print("You must initialize the relay before you can use it")