press(key) does not always work

[256shadesofgrey]

I am trying to write a script that intercepts some keys and replaces their input. Because I cannot suppress individual keys, I wrote a "pass-through" for all keys that are not my hotkeys:

from pynput import keyboard
from pynput.keyboard import Key

kc = keyboard.Controller()
ignore_press = False
ignore_release = False

def on_press(key):
  # Make sure we don't intercept the key we just sent.
  global ignore_press
  if ignore_press:
    ignore_press = False
    return
  ignore_press = True

  try:
    kc.press(key.char)
  except AttributeError:
    kc.press(key)


def on_release(key):
  # Make sure we don't intercept the key we just sent.
  global ignore_release
  if ignore_release:
    ignore_release = False
    return
  ignore_release = True

  try:
    kc.release(key.char)
  except AttributeError:
    kc.release(key)


with keyboard.Listener(on_press=on_press, on_release=on_release, suppress=True) as listener:
  listener.join()

Now if I try to type, this works for all the keys that do not cause an AttributeError when trying to access key.char. But any key that does not have a .char (i.e. space, backspace, enter) will simply have no effect.

However if I just directly try to press() the key, it does work:

from pynput import keyboard
from pynput.keyboard import Key
from time import sleep

kc = keyboard.Controller()

sleep(3)
kc.press(Key.backspace)
kc.release(Key.backspace)

Sleep is here just to have time to switch to an editor to test the input.

I'm doing this on linux with xorg. Haven't tested it anywhere else.