python - How can I stop a character in pygame from leaving the edge of the screen?

Question

I have created a small program in pygame where the player controls a blue square moving around the screen, but I want to stop the player from moving past the edge of the screen. Here is the code I have so far, how can I do this?

import pygame

pygame.init()
screen = pygame.display.set_mode((800, 600))
done = False
x = 30
y = 30

clock = pygame.time.Clock()

while not done:
        for event in pygame.event.get():
                if event.type == pygame.QUIT:
                        done = True
                if event.type == pygame.KEYDOWN and event.key == pygame.K_SPACE:
                        is_blue = not is_blue


    pressed = pygame.key.get_pressed()
    if pressed[pygame.K_UP]: y -= 5
    if pressed[pygame.K_DOWN]: y += 5
    if pressed[pygame.K_LEFT]: x -= 5
    if pressed[pygame.K_RIGHT]: x += 5

    screen.fill((0, 0, 0))
    color = (0, 128, 255)
    pygame.draw.rect(screen, color, pygame.Rect(x, y, 60, 60))

    pygame.display.flip()
    clock.tick(60)

Answer 1

pygame.Rects have a clamp (and clamp_ip) method which you can use to limit the movement area. So create a rect with the size of the screen (called screen_rect here) and a rect for the player (player_rect) and call the clamp_ip method after each movement to keep it inside of the screen area.

import pygame as pg


pg.init()
screen = pg.display.set_mode((640, 480))
BG_COLOR = pg.Color(30, 30, 50)


def main():
    clock = pg.time.Clock()
    image = pg.Surface((50, 30))
    image.fill(pg.Color('dodgerblue'))
    pg.draw.rect(image, pg.Color(40, 220, 190), (0, 0, 49, 29), 2)
    player_rect = image.get_rect(topleft=(200, 200))
    # This pygame.Rect has the dimensions of the screen and
    # is used to clamp the player_rect to this area.
    screen_rect = screen.get_rect()
    speed = 5

    while True:
        for event in pg.event.get():
            if event.type == pg.QUIT:
                return

        pressed = pg.key.get_pressed()
        if pressed[pg.K_UP]:
            player_rect.y -= speed
        if pressed[pg.K_DOWN]:
            player_rect.y += speed
        if pressed[pg.K_LEFT]:
            player_rect.x -= speed
        if pressed[pg.K_RIGHT]:
            player_rect.x += speed
        # Clamp the rect to the dimensions of the screen_rect.
        player_rect.clamp_ip(screen_rect)

        screen.fill(BG_COLOR)
        screen.blit(image, player_rect)

        pg.display.flip()
        clock.tick(60)


if __name__ == '__main__':
    main()
    pg.quit()