Finally the Event Loop
This is the final part of the game. All the implementations, class definitions and variable declarations have lead to this point. This is the final stretch so just stay with me for just a few more lines of code and we are done
So there are things that we would need before we define the game’s event loop We would need to define some variables
We need to define the wait_time which is used to stall the event loop for a certain amount of frames.
wait_time = 0
We need to define the running, left_paddle, right_paddle and ball variables
running = True
left_paddle = Player(-10)
right_paddle = Player(screen_width-10)
ball = Ball()
We define the left_paddle to have an initial x location of -10 and we define the right_paddle to have an initial x location of screen_width - 10
Since we have all of our variables defined we can then talk about the event loop
The event loop for this game would execute the following sequentially every frame
- Check for the quit event and any keyboard events
- Draw the background color
- Draw the ball, left paddle and the right paddle
- Draw the two players score
- Update the location of the two paddles if there are any updates
- Check for collisions
- Update the location of the ball
And that’s all the event loop will execute multiple times per second.
So let’s start by defining it one by one
For the first step, we need to get all the events and check if there is a quit event. If there is one then we break out of the loop and quit pygame
while running:
# ? We first get all the events that pygame is giving us
for e in pygame.event.get():
# ? We checked if the player wants to quit the game
if e.type == pygame.QUIT:
# ? This breaks out the event loop and then quits the game
running = False
pygame.quit()
Then we need to check for the KEYDOWN event and then change the moving variable to True and change the moving_up property of the paddle to True if it moving up
Then we can check for the KEYUP event and then change the moving property of the paddle back to False
The left paddle is controlled by w and s
The right paddle is controlled by Up and Down
We can implement it by doing
# ? This is where we do all of our input stuff for the game
# ? This checks if the player has pressed a key down
elif e.type == pygame.KEYDOWN:
# ? We check if we pressed the w key and say that the left paddle is moving up
if e.key == pygame.K_w:
left_paddle.moving = True
left_paddle.moving_up = True
# ? We check if we pressed the up key and say that the right paddle is moving up
elif e.key == pygame.K_UP:
right_paddle.moving = True
right_paddle.moving_up = True
# ? We check if we pressed the s key and say that the left paddle is moving down
elif e.key == pygame.K_s:
left_paddle.moving = True
left_paddle.moving_up = False
# ? We check if we pressed the down key and say that the right paddle is moving down
elif e.key == pygame.K_DOWN:
right_paddle.moving = True
right_paddle.moving_up = False
# ? This checks if the player has stopped pressing the any keys
elif e.type == pygame.KEYUP:
# ? We stop moving the left paddle when we release the w key
if e.key == pygame.K_w:
left_paddle.moving = False
# ? We stop moving the right paddle when we release the up key
elif e.key == pygame.K_UP:
right_paddle.moving = False
# ? We stop moving the left paddle when we release the s key
elif e.key == pygame.K_s:
left_paddle.moving = False
# ? We stop moving the right paddle when we release the down key
elif e.key == pygame.K_DOWN:
right_paddle.moving = False
The next step would just be put after the for loop that gets the events
# ? We fill the display with black background color
display.fill(background_color)
The next step is to show the ball and the two paddles
# ? We then show the ball and the paddles
ball.show()
left_paddle.show()
right_paddle.show()
show_score()
Then we move over to the next step which is to add the update functions and check collisions? RIght?
Yeah! But we need to not update when we wait_time is greater than 0.
We just say that we should check for movement updates and check for collisions when the wait_timer == 0. If it is not 0 we then minus one from the wait_timer
The snippet would look like this
# ? Ah! The wait timer
# ? This is a variable that we created when we defining some stuffs
# ? This basically pauses the game for some time
# ? We achieve this by not update the two paddles location and the ball locations and also by not checking collisions
if wait_timer == 0:
left_paddle.update()
right_paddle.update()
ball.check_collisions(left_paddle, right_paddle)
ball.update()
# ? If the timer is not zero it doesn't do anything at all
else:
# ? Then we count the decrement the timer by 1 every frame
wait_timer -= 1
Then we update the display
# ? This updates the display to then show the ball and the paddles
pygame.display.update()
And we then make the event loop run at the specified framerate
# ? This makes sure that the event loop runs at the specified frame rate
clock.tick(FRAMERATE)
And we are done with PONG!!!!!!!!!!!!.
So let’s look at the whole event loop.
# ? This creates the two paddles and ball object
left_paddle = Player(-10)
right_paddle = Player(screen_width-10)
ball = Ball()
# ? This is basically the event loop
# ? The order by which things are put things here matter a lot
# ? For the event loop we perform the following things
# ? -> Check the quit event and for any keyboard events
# ? -> Draw the background color
# ? -> Draw the paddles and the ball
# ? -> Draw the left and right score of the players
# ? -> Update the ball's position and the paddle's position
# ? -> Then we check for collisions between the ball, the screen and any of the paddles
# ? And then we repeat forever and ever
while running:
# ? We first get all the events that pygame is giving us
for e in pygame.event.get():
# ? We checked if the player wants to quit the game
if e.type == pygame.QUIT:
# ? This breaks out the event loop and then quits the game
running = False
pygame.quit()
sys.exit()
# ? This is where we do all of our input stuff for the game
# ? This checks if the player has pressed a key down
elif e.type == pygame.KEYDOWN:
# ? We check if we pressed the w key and say that the left paddle is moving up
if e.key == pygame.K_w:
left_paddle.moving = True
left_paddle.moving_up = True
# ? We check if we pressed the up key and say that the right paddle is moving up
elif e.key == pygame.K_UP:
right_paddle.moving = True
right_paddle.moving_up = True
# ? We check if we pressed the s key and say that the left paddle is moving down
elif e.key == pygame.K_s:
left_paddle.moving = True
left_paddle.moving_up = False
# ? We check if we pressed the down key and say that the right paddle is moving down
elif e.key == pygame.K_DOWN:
right_paddle.moving = True
right_paddle.moving_up = False
# ? This checks if the player has stopped pressing the any keys
elif e.type == pygame.KEYUP:
# ? We stop moving the left paddle when we release the w key
if e.key == pygame.K_w:
left_paddle.moving = False
# ? We stop moving the right paddle when we release the up key
elif e.key == pygame.K_UP:
right_paddle.moving = False
# ? We stop moving the left paddle when we release the s key
elif e.key == pygame.K_s:
left_paddle.moving = False
# ? We stop moving the right paddle when we release the down key
elif e.key == pygame.K_DOWN:
right_paddle.moving = False
# ? We fill the display with black background color
display.fill(background_color)
# ? We then show the ball and the paddles
ball.show()
left_paddle.show()
right_paddle.show()
show_score()
# ? Ah! The wait timer
# ? This is a variable that we created when we defining some stuffs
# ? This basically pauses the game for some time
# ? We achieve this by not update the two paddles location and the ball locations and also by not checking collisions
if wait_timer == 0:
left_paddle.update()
right_paddle.update()
ball.check_collisions(left_paddle, right_paddle)
ball.update()
# ? If the timer is not zero it doesn't do anything at all
else:
# ? Then we count the decrement the timer by 1 every frame
wait_timer -= 1
# ? This updates the display to then show the ball and the paddles
pygame.display.update()
# ? This makes sure that the event loop runs at the specified frame rate
clock.tick(FRAMERATE)
Now that we are done let’s look at our beautiful work at once in the next module.