Module 7 - Section 2 - Bitmap Graphics

7.2.5 - Moving sprites with the keyboard

As we have seen in a previous chapter we can use the keyboard to control the movement of shapes. The same thing can be done with sprites.

Save the avoid_v0.1 program as avoid_v0.2 inside the same folder Module7.2.

To move the spaceship

1. We initialize its position and speed outside the main loop with the following commands:

# Initialization of spaceships position and speed
ship_x = 380
ship_y = 285
ship_x_speed = 0
ship_y_speed = 0

2. Inside the main loop in the event processing area we add the commands:

        if event.type == pygame.KEYDOWN:
                if event.key == pygame.K_RIGHT or event.key == pygame.K_d:
                    ship_x_speed = 5
                if event.key == pygame.K_LEFT or event.key == pygame.K_a:
                    ship_x_speed = -5
                if event.key == pygame.K_DOWN or event.key == pygame.K_s:
                    ship_y_speed = 5
                if event.key == pygame.K_UP or event.key == pygame.K_w:
                    ship_y_speed = -5

        if event.type == pygame.KEYUP:
                if event.key == pygame.K_RIGHT or event.key == pygame.K_LEFT:
                    ship_x_speed = 0
                if event.key == pygame.K_d or event.key == pygame.K_a:
                    ship_x_speed = 0
                if event.key == pygame.K_UP or event.key == pygame.K_DOWN:
                    ship_y_speed = 0
                if event.key == pygame.K_w or event.key == pygame.K_s:
                    ship_y_speed = 0

3. In the game logic area we add the following commands so the spaceship which size is 40x33 doesn't get out of the screen.

    if ship_x >= 0 and ship_x <= 760:
        ship_x += ship_x_speed
    elif ship_x < 0:
        ship_x = 1
    elif ship_x > 760:
        ship_x = 759
    if ship_y >= 0 and ship_y <= 567:
        ship_y += ship_y_speed
    elif ship_y < 0:
        ship_y = 1
    elif ship_y > 567:
        ship_y = 566

4. and change the command that blit the spaceship using the variables ship_x and ship_y:

screen.blit(spaceshipImg, (ship_x, ship_y))

The final program can be downloaded from here.