gpiozero button callback running only once

Question

I'm getting started with a project on a Raspberry Pi (never done anything with RPi or python before, so it's all new to me, but I've done a little Arduino stuff). I'm trying to create a very simply python script to run a bit of code whenever a digital input signal switches from low to high or high to low.

I'm treating the input as a button, and using the gpiozero library. I'm trying to use the callback method to run my code whenever the transitions take place.

The problem is that the callback only happens once. I expect each callback to run every time I make or break contact on the switch, so I should see "pressed" and "released" printed N times if I toggle the switch N times. But instead I only see a single line printed, as though the callbacks are firing once and then just stopping. The script does not exit (because of the "pause" call at the end), so that's not the problem.

I've based my work on the examples in the gpiozero Recipes. There is an example (See 3rd codeblock under the "Button" heading) that is almost exactly what I need, and the description says "Run a function every time the button is pressed", but my code only runs the function once.

Perhaps I'm making some newbie RPi or Python mistake, but I'm stuck. Please help me out. Thanks.

Here is my code:

from gpiozero import Button
import signal

button = Button(3)

def pressed():
      print("pressed")

def released():
      print("released")


button.when_pressed = pressed
button.when_released = released
signal.pause()

Answer 1

I think the signal.pause() may be the issue.

Could you replace signal.pause() with the following?

import time
while True:
   time.sleep(1)

Alternatively perhaps you should try GPIO4. GPIO2 and GPIO3 have hard-wired pull-ups to 3V3. Does your button take this into account?

EDITED TO ADD

Given that both of the above variants work on my system perhaps your system is out of date.

Try updating the modules, e.g.

sudo apt-get update

sudo apt-get upgrade

If it still doesn't work try the following if your system is very old

sudo apt-get dist-upgrade