clicking a button attached to pin 7 sends space character, used with photo booth software to signal to take a picture.

main.py

# Itsy Bitsy M0 Express spacebar button
# With CircuitPython 3.0

import board
import gc
import time
from digitalio import DigitalInOut, Direction, Pull
import adafruit_dotstar


gc.collect()   # make some rooooom
# HID keyboard support
from adafruit_hid.keyboard import Keyboard
from adafruit_hid.keycode import Keycode

# One pixel connected internally!
dot = adafruit_dotstar.DotStar(board.APA102_SCK, board.APA102_MOSI, 1, brightness=0.5)

# Digital input with pullup on D7
buttons = []
for p in [board.D7,]:
    button = DigitalInOut(p)
    button.direction = Direction.INPUT
    button.pull = Pull.UP
    buttons.append(button)

# Used if we do HID output, see below
kbd = Keyboard()

######################### HELPERS ##############################

# Helper to give us a nice color swirl
def wheel(pos):
    # Input a value 0 to 255 to get a color value.
    # The colours are a transition r - g - b - back to r.
    if (pos < 0):
        return [0, 0, 0]
    if (pos > 255):
        return [0, 0, 0]
    if (pos < 85):
        return [int(pos * 3), int(255 - (pos*3)), 0]
    elif (pos < 170):
        pos -= 85
        return [int(255 - pos*3), 0, int(pos*3)]
    else:
        pos -= 170
        return [0, int(pos*3), int(255 - pos*3)]
    
######################### MAIN LOOP ##############################

i = 0
while True:
  # spin internal LED around! autoshow is on
  dot[0] = wheel(i & 255)

  if not buttons[0].value:
      #print("Button D7 pressed!", end ="\t")
      kbd.press(Keycode.SPACE)
      kbd.release_all()
      time.sleep(2)
      print("")
      #kbd.press(Keycode.A)
      kbd.release_all()

  i = (i+1) % 256  # run from 0 to 255
  #time.sleep(0.01) # make bigg   er to slow down

got rid of a lot of left over code from the demos this was taken from.