🛠 Premier script Python : faire clignoter la LED

Objectives

Write and run your first Python 3 script on the Raspberry Pi 2: a loop that blinks an LED, with a counter and clean shutdown. You will learn how to create a file, make it executable, handle Ctrl+C, and use the gpiozero library, the simplest one for beginners.

Hardware

• Raspberry Pi 2 Model B running 32-bit Raspberry Pi OS
• LED + 330 Ω resistor on GPIO17 (as in the LED tutorial)
• Package: sudo apt install python3-gpiozero

Complete code

#!/usr/bin/env python3
"""blink.py — fait clignoter une LED sur GPIO17 avec gpiozero."""
from gpiozero import LED
from time import sleep

led = LED(17)  # broche BCM17 du connecteur J8

def on:
    print("LED allumee")

def off:
    print("LED eteinte")

led.when_on = on
led.when_off = off

try:
    for i in range(10):
        print(f"Cycle {i + 1}/10")
        led.on
        sleep(0.5)
        led.off
        sleep(0.5)
    print("Termine")
except KeyboardInterrupt:
    led.close
    print("Arrete proprement")

Expected verification

The LED blinks once per second (0.5 s on, 0.5 s off) for 10 cycles, and the terminal displays each cycle. Ctrl+C displays "Stopped cleanly" and turns off the LED. Since the Pi 2 is quad-core (4× Cortex-A7 at 900 MHz), the script remains very lightweight: a single core is more than sufficient.

Common errors

• gpiozero module not found: install python3-gpiozero, not the old Python 2 package.
• Permission denied on the GPIO: on recent kernels, add your user to the gpio group or run with sudo.
• Incorrect pin number: gpiozero uses BCM numbering; physical pin 11 corresponds to GPIO17.
• The LED stays on after Ctrl+C: you must call led.close to release the pin.