Button press detection in Raspberry Pi

Introduction

We use button press detection to know when someone presses a physical button connected to the Raspberry Pi. This helps the Pi react to user actions.

You want to turn on an LED when a button is pressed.

You want to start or stop a program by pressing a button.

You want to count how many times a button is pressed.

You want to control a robot or device with button presses.

Syntax

Raspberry Pi

import RPi.GPIO as GPIO
import time

button_pin = 18
GPIO.setmode(GPIO.BCM)
GPIO.setup(button_pin, GPIO.IN, pull_up_down=GPIO.PUD_UP)

while True:
    if GPIO.input(button_pin) == GPIO.LOW:
        print("Button pressed")
        time.sleep(0.2)  # debounce delay

Use GPIO.setup() to set the button pin as input with a pull-up resistor.

Button press is detected when the input reads GPIO.LOW because the button connects the pin to ground.

Examples

Check once if the button is pressed.

Raspberry Pi

import RPi.GPIO as GPIO

button_pin = 18
GPIO.setmode(GPIO.BCM)
GPIO.setup(button_pin, GPIO.IN, pull_up_down=GPIO.PUD_UP)

if GPIO.input(button_pin) == GPIO.LOW:
    print("Button is pressed")

Keep checking the button in a loop and print when pressed.

Raspberry Pi

import RPi.GPIO as GPIO
import time

button_pin = 18
GPIO.setmode(GPIO.BCM)
GPIO.setup(button_pin, GPIO.IN, pull_up_down=GPIO.PUD_UP)

while True:
    if GPIO.input(button_pin) == GPIO.LOW:
        print("Button pressed")
        time.sleep(0.3)  # wait to avoid multiple prints

Sample Program

This program waits for the button press and prints a message each time you press it. It cleans up the GPIO pins when you stop the program.

Raspberry Pi

import RPi.GPIO as GPIO
import time

button_pin = 18

GPIO.setmode(GPIO.BCM)
GPIO.setup(button_pin, GPIO.IN, pull_up_down=GPIO.PUD_UP)

print("Press the button...")

try:
    while True:
        if GPIO.input(button_pin) == GPIO.LOW:
            print("Button pressed!")
            time.sleep(0.5)  # debounce delay
except KeyboardInterrupt:
    print("Program stopped")
finally:
    GPIO.cleanup()

Important Notes

Use GPIO.cleanup() to reset pins when done.

Adding a small delay after detecting a press helps avoid multiple detections from one press (called debounce).

Summary

Button press detection lets your Raspberry Pi respond to physical button presses.

Set the button pin as input with a pull-up resistor and check for GPIO.LOW to detect presses.

Use a loop and a small delay to detect presses continuously and avoid false triggers.