🛠 Premier script Python sur le Pi

Objectives

Write, make executable, and run a first Python 3 script on the Raspberry Pi 3 Model B. Understand the shebang (#!/usr/bin/env python3), execution permissions (chmod +x), and control the LED from the previous tutorial using Python with gpiozero (preinstalled on Raspberry Pi OS). This is the foundation for all the automations we will run as systemd services later.

Hardware

• Raspberry Pi 3 Model B running Raspberry Pi OS Lite (Python 3 included)
• LED + 330 Ω resistor on GPIO17 (physical pin 11), as in tutorial 1
• nano editor (included) and SSH terminal
• No libraries to install: gpiozero is preinstalled

Complete Code

#!/usr/bin/env python3
"""clignot.py — premier script : message console + LED sur GPIO17.
   gpiozero est préinstallé sur Raspberry Pi OS (Pi 3B inclus)."""
from gpiozero import LED
from time import sleep

led = LED(17)  # BCM17 = broche physique 11 (logique 3,3 V)

print("Bonjour depuis le Raspberry Pi 3 Model B !")

for i in range(5):
    led.on
    print(f"Cycle {i + 1} : LED allumée")
    sleep(0.2)
    led.off
    sleep(0.3)

print("Terminé.")

Save as clignot.py, then:

chmod +x clignot.py   # droit d'exécution
./clignot.py          # lancer depuis le dossier courant

Expected Verification

The terminal displays "Hello from the Raspberry Pi 3 Model B!" followed by the 5 cycle lines, while the LED blinks (200 ms on, 300 ms off). The script terminates cleanly with "Done.". Rerunning with python3 clignot.py must yield exactly the same result — the shebang is just a shortcut.

Common Errors

• Permission denied when running ./clignot.py: forgetting chmod +x — or the file was created on an SD card mounted as FAT from Windows.
• bad interpreter: file written with Windows line endings (CRLF); fix with dos2unix clignot.py.
• ModuleNotFoundError: gpiozero: on a third-party distribution (Ubuntu, Alpine), install python3-gpiozero or run pip install gpiozero.
• RuntimeError: No suitable pin factory: running as root without a graphical environment; on Raspberry Pi OS Lite, keep gpiozero defaults and avoid unnecessary sudo.
• Mixed Python indentation (spaces/tabs): nano may paste tabs, prefer 4 spaces.
• Forgetting that GPIO17 is 3.3 V: never connect a 5 V input to the pin.