Keyboard Input — Arrow Keys

By the end of this lesson you can:

• Move a player actor left and right by checking keyboard.left and keyboard.right inside update(dt).
• Clamp the player at the screen edges so it cannot walk off-screen.
• Use on_key_down(key) to trigger a one-shot action (for example, printing a message when SPACE is pressed).

Think about how a game uses the keyboard. Which actions need a held key and which need a single press?

• Walking left: you hold the key until you stop.
• Jumping: one press, one jump — holding the key should not make you jump forever.
• Firing a bullet: one press fires one bullet.

Pygame Zero gives us two tools for these two situations. Which should you use for each?

Think of keyboard as a dictionary of switches — each key is either True (held down) or False (released). Checking it in update() means you read it 60 times a second, producing smooth continuous movement.

Held movement in update()

def update(dt):
    if keyboard.left:
        player.x -= 200 * dt
    if keyboard.right:
        player.x += 200 * dt

Both checks are independent if statements (not elif), so pressing left and right simultaneously cancels out — the player stays still, which feels natural.

Clamping at the edges

Add boundary checks after the movement so the player cannot walk off screen:

    if player.x < 0:
        player.x = 0
    if player.x > WIDTH:
        player.x = WIDTH

Up and down

keyboard.up and keyboard.down work exactly the same way for vertical movement. You can also use letter keys: keyboard.a (left), keyboard.d (right), keyboard.w (up), keyboard.s (down) — common in PC games.

One-shot actions with on_key_down

on_key_down is a hook function — define it and Pygame Zero calls it once per key press:

def on_key_down(key):
    if key == keys.SPACE:
        print("Jump!")

keys.SPACE, keys.LEFT, keys.UP are the named constants for special keys. Note: keys (plural) is used for the constant, while keyboard (singular) is for held state.

Why it matters

Player input is what turns a animation into a game. Every game you have ever played uses exactly this pattern: held keys for movement, single-press keys for actions. Mastering it here means every future game you build already has working controls.

The story

Faiz wants to control his character with the arrow keys, left and right. The character should not be able to walk off the screen. Press SPACE to wave. Save as faiz_moves.py:

# faiz_moves.py — arrow key movement with clamping

import pgzrun

WIDTH = 600
HEIGHT = 400
TITLE = "Faiz Moves!"

player = Actor("alien")
player.x = 300
player.y = 340

def draw():
    screen.fill("skyblue")
    player.draw()
    screen.draw.text(
        "← → to move   SPACE to wave",
        center=(WIDTH // 2, 20),
        fontsize=20,
        color="black",
    )

def update(dt):
    if keyboard.left:
        player.x -= 220 * dt
    if keyboard.right:
        player.x += 220 * dt
    if player.x < 0:
        player.x = 0
    if player.x > WIDTH:
        player.x = WIDTH

def on_key_down(key):
    if key == keys.SPACE:
        print("Faiz waves hello!")

pgzrun.go()

What you will see

Try holding both arrow keys simultaneously — the player stays still because both movement additions cancel out.

Check keyboard.left / keyboard.right inside update(dt) for smooth held movement. Always clamp the player's position afterwards. For actions that should fire once per press, define on_key_down(key) and compare against keys.SPACE or other constants.