GPIO cleanup on exit in Raspberry Pi - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output when GPIO cleanup is called?

Consider this Python code running on a Raspberry Pi using the RPi.GPIO library. What will be printed when the program exits?

Raspberry Pi

import RPi.GPIO as GPIO
import time

GPIO.setmode(GPIO.BCM)
GPIO.setup(18, GPIO.OUT)

try:
    GPIO.output(18, GPIO.HIGH)
    print("LED ON")
    time.sleep(1)
finally:
    GPIO.cleanup()
    print("GPIO cleaned up")

A LED ON

B No output

C GPIO cleaned up

D LED ON\nGPIO cleaned up

💡 Hint

Look at what happens in the finally block after the try block.

The try block prints 'LED ON'. The finally block always runs and calls GPIO.cleanup(), then prints 'GPIO cleaned up'. So both lines print in order.

❓ Predict Output

intermediate

What happens if GPIO.cleanup() is omitted?

What is the likely effect if a Raspberry Pi Python script using GPIO pins does NOT call GPIO.cleanup() before exiting?

A GPIO pins remain set and may cause warnings on next run

B Program crashes immediately with an error

C GPIO pins reset automatically with no issues

D The Raspberry Pi shuts down

💡 Hint

Think about what happens to GPIO pin states after the program ends.

Without cleanup, pins stay configured and may cause warnings or unexpected behavior next time GPIO is used.

🔧 Debug

advanced

Identify the error preventing GPIO cleanup on exit

This code aims to clean up GPIO pins on program exit but fails to do so. What is the error?

Raspberry Pi

import RPi.GPIO as GPIO
import time

GPIO.setmode(GPIO.BCM)
GPIO.setup(17, GPIO.OUT)

try:
    GPIO.output(17, GPIO.HIGH)
    time.sleep(2)
except KeyboardInterrupt:
    print("Interrupted")
finally:
    GPIO.cleanup()
    print("Cleanup done")

A The except block should be after finally

B GPIO.cleanup is missing parentheses, so cleanup is not called

C time.sleep should be inside finally block

D GPIO.setup is called after setmode, which is incorrect

💡 Hint

Check how functions are called in Python.

GPIO.cleanup is a function and must be called with parentheses: GPIO.cleanup()

🧠 Conceptual

advanced

Why use try-finally for GPIO cleanup?

Why is it recommended to use a try-finally block when working with GPIO pins in Python on Raspberry Pi?

A To ensure GPIO.cleanup() runs even if an error or interrupt occurs

B To speed up the GPIO pin setup process

C To prevent the program from printing output

D To automatically detect hardware failures

💡 Hint

Think about what finally blocks guarantee in Python.

The finally block always runs, so cleanup happens even if the program crashes or is interrupted.

❓ Predict Output

expert

What is the output of this GPIO cleanup signal handler code?

This Python code sets a signal handler to clean up GPIO on Ctrl+C. What will be printed when the user presses Ctrl+C?

Raspberry Pi

import RPi.GPIO as GPIO
import signal
import sys

GPIO.setmode(GPIO.BCM)
GPIO.setup(22, GPIO.OUT)

GPIO.output(22, GPIO.HIGH)
print("LED ON")

def cleanup_handler(sig, frame):
    GPIO.cleanup()
    print("Cleaned up and exiting")
    sys.exit(0)

signal.signal(signal.SIGINT, cleanup_handler)

print("Press Ctrl+C to exit")
while True:
    pass

A Press Ctrl+C to exit\nCleaned up and exiting

B LED ON\nCleaned up and exiting

C LED ON\nPress Ctrl+C to exit\nCleaned up and exiting

D No output

💡 Hint

Consider the order of print statements and when the signal handler runs.

The program prints 'LED ON' then 'Press Ctrl+C to exit'. When Ctrl+C is pressed, the handler prints 'Cleaned up and exiting' before exiting.