5.3 Keyboard input and moving a rect

We’ll read the keyboard and move our rectangle so we can control something on screen (like a player or a cursor).

Events and KEYDOWN

Inside the game loop we get events. When the user presses a key, we get an event with event.type == pygame.KEYDOWN. The key is in event.key. Pygame gives each key a constant, e.g. pygame.K_UP, pygame.K_DOWN, pygame.K_LEFT, pygame.K_RIGHT, pygame.K_SPACE, pygame.K_a, etc.

Printing the key (for testing)

You can print which key was pressed to check it works:

while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_UP:
                print("UP")
            if event.key == pygame.K_DOWN:
                print("DOWN")
            if event.key == pygame.K_LEFT:
                print("LEFT")
            if event.key == pygame.K_RIGHT:
                print("RIGHT")

Moving a rect with the arrow keys

Create a rect, then in the KEYDOWN block change its position. Remember: decreasing y moves up (y-axis is flipped), so for “up” we do rect.y -= 1. For “down”, rect.y += 1. Left/right: decrease x for left, increase for right.

Example:

rect = pygame.Rect((200, 200), (20, 20))

while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_UP:
                rect.y -= 10   # move up (smaller y)
            if event.key == pygame.K_DOWN:
                rect.y += 10
            if event.key == pygame.K_LEFT:
                rect.x -= 10
            if event.key == pygame.K_RIGHT:
                rect.x += 10

    screen.fill((0, 0, 0))
    pygame.draw.rect(screen, (255, 0, 0), rect)
    pygame.display.flip()

Using rect.y -= 10 is the same as rect.y = rect.y - 10 — just shorter. You can use a variable like speed = 5 and then rect.x += speed to make tuning movement easier.

Keeping the rect on screen (optional)

You can clamp the rect so it doesn’t go off the edges using clamp():

rect.clamp_ip(screen.get_rect())

That keeps the rect fully inside the screen.

Project: Move a square

1. Start from your “square on screen” program.
2. Add KEYDOWN handling for the four arrow keys and move the rect (e.g. by 10 pixels per press).
3. Redraw the rect every frame (fill then draw then flip).
4. Optionally use clamp_ip so the square can’t leave the window.

Once this works, you’ve got a controllable character — next we add collision so it can interact with obstacles.

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Next: 5.4 Collision and game logic — when two rects touch.