Raspberry Pi 4 GPIO Basics with gpiozero: LEDs, Buttons and a Buzzer

#!/usr/bin/env python3
# crossing.py - pedestrian crossing on a Raspberry Pi 4 using gpiozero
# Wiring (BCM numbers): red=17, amber=27, green=22, button=23, buzzer=24
from gpiozero import TrafficLights, Button, Buzzer
from signal import pause
from threading import Event, Thread
from time import sleep

# TrafficLights groups three LEDs: red, amber, green
lights = TrafficLights(red=17, amber=27, green=22)
# Button uses the internal pull-up; bounce_time ignores contact bounce
button = Button(23, bounce_time=0.05)
buzzer = Buzzer(24)

request = Event()   # set when a pedestrian presses the button

def on_press():
    """Called by gpiozero in a background thread on every press."""
    print('Crossing requested')
    request.set()

button.when_pressed = on_press

def controller():
    """Main traffic sequence, runs forever in its own thread."""
    while True:
        # Traffic flows: green for vehicles
        lights.green.on()
        request.wait()          # block here until someone presses the button
        sleep(2)                # small delay before stopping traffic

        # Green -> amber -> red for vehicles
        lights.green.off()
        lights.amber.on()
        sleep(2)
        lights.amber.off()
        lights.red.on()

        # Pedestrians cross: buzzer beeps 0.2 s on, 0.2 s off, 15 times (6 s)
        buzzer.beep(on_time=0.2, off_time=0.2, n=15, background=False)

        # Warning phase: flash amber before giving traffic green again
        lights.red.off()
        lights.amber.blink(on_time=0.3, off_time=0.3, n=6, background=False)

        request.clear()         # ignore presses made during the crossing

Thread(target=controller, daemon=True).start()
print('Running. Press Ctrl+C to stop.')
try:
    pause()                     # keep the main thread alive
except KeyboardInterrupt:
    print('Stopping')
finally:
    lights.off()
    buzzer.off()