Why don't arrow keys trigger Pygame KEYDOWN?

They do trigger; you're checking event.unicode (empty for non-printable). Use event.key against pygame.K_LEFT, K_RIGHT, K_UP, K_DOWN.

event.key vs event.unicode?

event.key: integer keycode (K_a, K_LEFT etc). event.unicode: character string for printable. Both populated; pick by need.

event.mod bitfield: KMOD_SHIFT, KMOD_CTRL etc. AND with desired modifier. pygame.key.get_mods() for current state.

Fix: Pygame KEYDOWN Doesn't Fire Arrow Keys

Quick answer: Compare event.key == pygame.K_LEFT. event.unicode is empty for non-printable.

Arrow key UI navigation. event.unicode check returns empty. KEYDOWN fires; you're reading the wrong attribute.

The Fix

for event in pygame.event.get():
    if event.type == pygame.KEYDOWN:
        if event.key == pygame.K_LEFT:
            move_left()
        elif event.key == pygame.K_RIGHT:
            move_right()
        elif event.unicode == "a":
            # printable only
            type_a()

event.key for keycodes (printable + special). event.unicode for printable text input. Don’t mix.

Verifying

Arrow keys move; printable keys type. Both work in same loop.

“event.key for codes. event.unicode for text.”

Related Issues

For event loop lag, see event lag. For mousewheel, see mousewheel.

event.key. Arrows fire.