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The PyGame library is an open-source module for the Python programming language specifically intended to help you make games and other multimedia applications. In this post, you'll learn how to use PyGame to write games in Python.
By the end of this article, you’ll be able to:
Table of Contents
pygame is a Python wrapper for the SDL library, which stands for Simple DirectMedia Layer. SDL provides cross-platform access to your system’s underlying multimedia hardware components, such as sound, video, mouse, keyboard, and joystick.
pygame started life as a replacement for the stalled PySDL project. The cross-platform nature of both SDL and
pygame means you can write games and rich multimedia Python programs for every platform that supports them!
pygame on your platform, use the appropriate
$ pip install pygame
You can verify the install by loading one of the examples that comes with the library:
$ python3 -m pygame.examples.aliens
If a game window appears, then
pygame is installed properly! If you run into problems, then the Getting Started guide outlines some known issues and caveats for all platforms.
Before getting down to specifics, let’s take a look at a basic
pygame program. This program creates a window, fills the background with white, and draws a blue circle in the middle of it:
# Simple pygame program # Import and initialize the pygame library import pygame pygame.init() # Set up the drawing window screen = pygame.display.set_mode([500, 500]) # Run until the user asks to quit running = True while running: # Did the user click the window close button? for event in pygame.event.get(): if event.type == pygame.QUIT: running = False # Fill the background with white screen.fill((255, 255, 255)) # Draw a solid blue circle in the center pygame.draw.circle(screen, (0, 0, 255), (250, 250), 75) # Flip the display pygame.display.flip() # Done! Time to quit. pygame.quit()
When you run this program, you’ll see a window that looks like this:
Let’s break this code down, section by section:
pygamelibrary. Without these lines, there is no
pygame.QUIT, which occurs when the user clicks the window close button.
screen.fill()accepts either a list or tuple specifying the RGB values for the color. Since
(255, 255, 255)was provided, the window is filled with white.
screen: the window on which to draw
(0, 0, 255): a tuple containing RGB color values
(250, 250): a tuple specifying the center coordinates of the circle
75: the radius of the circle to draw in pixels
pygame. This only happens once the loop finishes.
pygame version of “Hello, World.” Now let’s dig a little deeper into the concepts behind this code.
pygame and the SDL library are portable across different platforms and devices, they both need to define and work with abstractions for various hardware realities. Understanding those concepts and abstractions will help you design and develop your own games.
pygame library is composed of a number of Python constructs, which include several different modules. These modules provide abstract access to specific hardware on your system, as well as uniform methods to work with that hardware. For example,
display allows uniform access to your video display, while
joystick allows abstract control of your joystick.
After importing the
pygame library in the example above, the first thing you did was initialize PyGame using
pygame.init(). This function calls the separate
init() functions of all the included
pygame modules. Since these modules are abstractions for specific hardware, this initialization step is required so that you can work with the same code on Linux, Windows, and Mac.
In addition to the modules,
pygame also includes several Python classes, which encapsulate non-hardware dependent concepts. One of these is the
Surface which, at its most basic, defines a rectangular area on which you can draw.
Surface objects are used in many contexts in
pygame. Later you’ll see how to load an image into a
Surface and display it on the screen.
pygame, everything is viewed on a single user-created
display, which can be a window or a full screen. The display is created using
.set_mode(), which returns a
Surface representing the visible part of the window. It is this
Surface that you pass into drawing functions like
pygame.draw.circle(), and the contents of that
Surface are pushed to the display when you call
pygame program drew a shape directly onto the display’s
Surface, but you can also work with images on the disk. The
image module allows you to load and save images in a variety of popular formats. Images are loaded into
Surface objects, which can then be manipulated and displayed in numerous ways.
As mentioned above,
Surface objects are represented by rectangles, as are many other objects in
pygame, such as images and windows. Rectangles are so heavily used that there is a special
Rect class just to handle them. You’ll be using
Rect objects and images in your game to draw players and enemies, and to manage collisions between them.
Okay, that’s enough theory. Let’s design and write a game!Basic Game Design
Before you start writing any code, it’s always a good idea to have some design in place. Since this is a tutorial game, let’s design some basic gameplay for it as well:
When he was describing software projects, a former colleague of mine used to say, “You don’t know what you do until you know what you don’t do.” With that in mind, here are some things that won’t be covered in this tutorial:
You’re free to try your hand at adding these and other features to your own program.
Let’s get started!
After you import
pygame, you’ll also need to initialize it. This allows
pygame to connect its abstractions to your specific hardware:
# Import the pygame module import pygame # Import pygame.locals for easier access to key coordinates # Updated to conform to flake8 and black standards from pygame.locals import ( K_UP, K_DOWN, K_LEFT, K_RIGHT, K_ESCAPE, KEYDOWN, QUIT, ) # Initialize pygame pygame.init()
pygame library defines many things besides modules and classes. It also defines some local constants for things like keystrokes, mouse movements, and display attributes. You reference these constants using the syntax
pygame.<CONSTANT>. By importing specific constants from
pygame.locals, you can use the syntax
<CONSTANT> instead. This will save you some keystrokes and improve overall readability.
Now you need something to draw on! Create a screen to be the overall canvas:
# Import the pygame module import pygame # Import pygame.locals for easier access to key coordinates # Updated to conform to flake8 and black standards from pygame.locals import ( K_UP, K_DOWN, K_LEFT, K_RIGHT, K_ESCAPE, KEYDOWN, QUIT, ) # Initialize pygame pygame.init() # Define constants for the screen width and height SCREEN_WIDTH = 800 SCREEN_HEIGHT = 600 # Create the screen object # The size is determined by the constant SCREEN_WIDTH and SCREEN_HEIGHT screen = pygame.display.set_mode((SCREEN_WIDTH, SCREEN_HEIGHT))
You create the screen to use by calling
pygame.display.set_mode() and passing a tuple or list with the desired width and height. In this case, the window is 800x600, as defined by the constants
SCREEN_HEIGHT on lines 20 and 21. This returns a
Surface which represents the inside dimensions of the window. This is the portion of the window you can control, while the OS controls the window borders and title bar.
If you run this program now, then you’ll see a window pop up briefly and then immediately disappear as the program exits. Don’t blink or you might miss it! In the next section, you’ll focus on the main game loop to ensure that your program exits only when given the correct input.
Every game from Pong to Fortnite uses a game loop to control gameplay. The game loop does four very important things:
Every cycle of the game loop is called a frame, and the quicker you can do things each cycle, the faster your game will run. Frames continue to occur until some condition to exit the game is met. In your design, there are two conditions that can end the game loop:
The first thing the game loop does is process user input to allow the player to move around the screen. Therefore, you need some way to capture and process a variety of input. You do this using the
pygame event system.
Key presses, mouse movements, and even joystick movements are some of the ways in which a user can provide input. All user input results in an event being generated. Events can happen at any time and often (but not always) originate outside the program. All events in
pygame are placed in the event queue, which can then be accessed and manipulated. Dealing with events is referred to as handling them, and the code to do so is called an event handler.
Every event in
pygame has an event type associated with it. For your game, the event types you’ll focus on are keypresses and window closure. Keypress events have the event type
KEYDOWN, and the window closure event has the type
QUIT. Different event types may also have other data associated with them. For example, the
KEYDOWN event type also has a variable called
key to indicate which key was pressed.
You access the list of all active events in the queue by calling
pygame.event.get(). You then loop through this list, inspect each event type, and respond accordingly:
# Variable to keep the main loop running running = True # Main loop while running: # Look at every event in the queue for event in pygame.event.get(): # Did the user hit a key? if event.type == KEYDOWN: # Was it the Escape key? If so, stop the loop. if event.key == K_ESCAPE: running = False # Did the user click the window close button? If so, stop the loop. elif event.type == QUIT: running = False
Let’s take a closer look at this game loop:
running = False. The game loop starts on line 29.
KEYDOWNevent. If it is, then the program checks which key was pressed by looking at the
event.keyattribute. If the key is the Esc key, indicated by
K_ESCAPE, then it exits the game loop by setting
running = False.
QUIT. This event only occurs when the user clicks the window close button. The user may also use any other operating system action to close the window.
When you add these lines to the previous code and run it, you’ll see a window with a blank or black screen:
The window won’t disappear until you press the Esc key, or otherwise trigger a
QUIT event by closing the window.
In the sample program, you drew on the screen using two commands:
screen.fill()to fill the background
pygame.draw.circle()to draw a circle
Now you’ll learn about a third way to draw to the screen: using a
Recall that a
Surface is a rectangular object on which you can draw, like a blank sheet of paper. The
screen object is a
Surface, and you can create your own
Surface objects separate from the display screen. Let’s see how that works:
# Fill the screen with white screen.fill((255, 255, 255)) # Create a surface and pass in a tuple containing its length and width surf = pygame.Surface((50, 50)) # Give the surface a color to separate it from the background surf.fill((0, 0, 0)) rect = surf.get_rect()
After the screen is filled with white on line 45, a new
Surface is created on line 48. This
Surface is 50 pixels wide, 50 pixels tall, and assigned to
surf. At this point, you treat it just like the
screen. So on line, 51 you fill it with black. You can also access its underlying
.get_rect(). This is stored as
rect for later use.
Just creating a new
Surface isn’t enough to see it on the screen. To do that, you need to blit the
Surface onto another
Surface. The term
blit stands for Block Transfer, and
.blit() is how you copy the contents of one
Surface to another. You can only
.blit() from one
Surface to another, but since the screen is just another
Surface, that’s not a problem. Here’s how you draw
surf on the screen:
# This line says "Draw surf onto the screen at the center" screen.blit(surf, (SCREEN_WIDTH/2, SCREEN_HEIGHT/2)) pygame.display.flip()
.blit() call on line 55 takes two arguments:
(SCREENWIDTH/2, SCREENHEIGHT/2) tell your program to place
surf in the exact center of the screen, but it doesn’t quite look that way:
The reason why the image looks off-center is that
.blit() puts the top-left corner of
surf at the location given. If you want
surf to be centered, then you’ll have to do some math to shift it up and to the left. You can do this by subtracting the width and height of
surf from the width and height of the screen, dividing each by 2 to locate the center, and then passing those numbers as arguments to
# Put the center of surf at the center of the display surf_center = ( (SCREEN_WIDTH-surf.get_width())/2, (SCREEN_HEIGHT-surf.get_height())/2 ) # Draw surf at the new coordinates screen.blit(surf, surf_center) pygame.display.flip()
Notice the call to
pygame.display.flip() after the call to
blit(). This updates the entire screen with everything that’s been drawn since the last flip. Without the call to
.flip(), nothing is shown.
In your game design, the player starts on the left, and obstacles come in from the right. You can represent all the obstacles with
Surface objects to make drawing everything easier, but how do you know where to draw them? How do you know if an obstacle has collided with the player? What happens when the obstacle flies off the screen? What if you want to draw background images that also move? What if you want your images to be animated? You can handle all these situations and more with sprites.
In programming terms, a sprite is a 2D representation of something on the screen. Essentially, it’s a picture.
pygame provides a
Sprite class, which is designed to hold one or several graphical representations of any game object that you want to display on the screen. To use it, you create a new class that extends
Sprite. This allows you to use its built-in methods.
Here’s how you use
Sprite objects with the current game to define the player. Insert this code after line 18:
# Define a Player object by extending pygame.sprite.Sprite # The surface drawn on the screen is now an attribute of 'player' class Player(pygame.sprite.Sprite): def __init__(self): super(Player, self).__init__() self.surf = pygame.Surface((75, 25)) self.surf.fill((255, 255, 255)) self.rect = self.surf.get_rect()
You first define
Player by extending
pygame.sprite.Sprite on line 22. Then
.super() to call the
.__init__() method of
Next, you define and initialize
.surf to hold the image to display, which is currently a white box. You also define and initialize
.rect, which you’ll use to draw the player later. To use this new class, you need to create a new object and change the drawing code as well. Expand the code block below to see it all together:
Run this code. You’ll see a white rectangle at roughly the middle of the screen:
What do you think would happen if you changed line 59 to
screen.blit(player.surf, player.rect)? Try it and see:
# Fill the screen with black screen.fill((0, 0, 0)) # Draw the player on the screen screen.blit(player.surf, player.rect) # Update the display pygame.display.flip()
When you pass a
.blit(), it uses the coordinates of the top left corner to draw the surface. You’ll use this later to make your player move!
So far, you’ve learned how to set up
pygame and draw objects on the screen. Now, the real fun starts! You’ll make the player controllable using the keyboard.
Earlier, you saw that
pygame.event.get() returns a list of the events in the event queue, which you scan for
KEYDOWN event types. Well, that’s not the only way to read keypresses.
pygame also provides
pygame.event.get_pressed(), which returns a dictionary containing all the current
KEYDOWN events in the queue.
Put this in your game loop right after the event handling loop. This returns a dictionary containing the keys pressed at the beginning of every frame:
# Get the set of keys pressed and check for user input pressed_keys = pygame.key.get_pressed()
Next, you write a method in
Player to accepts that dictionary. This will define the behavior of the sprite based off the keys that are pressed. Here’s what that might look like:
# Move the sprite based on user keypresses def update(self, pressed_keys): if pressed_keys[K_UP]: self.rect.move_ip(0, -5) if pressed_keys[K_DOWN]: self.rect.move_ip(0, 5) if pressed_keys[K_LEFT]: self.rect.move_ip(-5, 0) if pressed_keys[K_RIGHT]: self.rect.move_ip(5, 0)
K_RIGHT correspond to the arrow keys on the keyboard. If the dictionary entry for that key is
True, then that key is down, and you move the player
.rect in the proper direction. Here you use
.move_ip(), which stands for move in place, to move the current
Then you can call
.update() every frame to move the player sprite in response to keypresses. Add this call right after the call to
# Main loop while running: # for loop through the event queue for event in pygame.event.get(): # Check for KEYDOWN event if event.type == KEYDOWN: # If the Esc key is pressed, then exit the main loop if event.key == K_ESCAPE: running = False # Check for QUIT event. If QUIT, then set running to false. elif event.type == QUIT: running = False # Get all the keys currently pressed pressed_keys = pygame.key.get_pressed() # Update the player sprite based on user keypresses player.update(pressed_keys) # Fill the screen with black screen.fill((0, 0, 0))
Now you can move your player rectangle around the screen with the arrow keys:
You may notice two small problems:
To keep the player on the screen, you need to add some logic to detect if the
rect is going to move off screen. To do that, you check whether the
rect coordinates have moved beyond the screen’s boundary. If so, then you instruct the program to move it back to the edge:
# Move the sprite based on user keypresses def update(self, pressed_keys): if pressed_keys[K_UP]: self.rect.move_ip(0, -5) if pressed_keys[K_DOWN]: self.rect.move_ip(0, 5) if pressed_keys[K_LEFT]: self.rect.move_ip(-5, 0) if pressed_keys[K_RIGHT]: self.rect.move_ip(5, 0) # Keep player on the screen if self.rect.left < 0: self.rect.left = 0 if self.rect.right > SCREEN_WIDTH: self.rect.right = SCREEN_WIDTH if self.rect.top <= 0: self.rect.top = 0 if self.rect.bottom >= SCREEN_HEIGHT: self.rect.bottom = SCREEN_HEIGHT
Here, instead of using
.move(), you just change the corresponding coordinates of
.right directly. Test this, and you’ll find the player rectangle can no longer move off the screen.
Now let’s add some enemies!
What’s a game without enemies? You’ll use the techniques you’ve already learned to create a basic enemy class, then create a lot of them for your player to avoid. First, import the
# Import random for random numbers import random
Then create a new sprite class called
Enemy, following the same pattern you used for
# Define the enemy object by extending pygame.sprite.Sprite # The surface you draw on the screen is now an attribute of 'enemy' class Enemy(pygame.sprite.Sprite): def __init__(self): super(Enemy, self).__init__() self.surf = pygame.Surface((20, 10)) self.surf.fill((255, 255, 255)) self.rect = self.surf.get_rect( center=( random.randint(SCREEN_WIDTH + 20, SCREEN_WIDTH + 100), random.randint(0, SCREEN_HEIGHT), ) ) self.speed = random.randint(5, 20) # Move the sprite based on speed # Remove the sprite when it passes the left edge of the screen def update(self): self.rect.move_ip(-self.speed, 0) if self.rect.right < 0: self.kill()
There are four notable differences between
rectto be a random location along the right edge of the screen. The center of the rectangle is just off the screen. It’s located at some position between 20 and 100 pixels away from the right edge, and somewhere between the top and bottom edges.
.speedas a random number between 5 and 20. This specifies how fast this enemy moves towards the player.
.update(). It takes no arguments since enemies move automatically. Instead,
.update()moves the enemy toward the left side of the screen at the
.speeddefined when it was created.
Enemyis fully off the screen and won’t just disappear while it’s still visible, you check that the right side of the
.recthas gone past the left side of the screen. Once the enemy is off-screen, you call
.kill()to prevent it from being processed further.
So, what does
.kill() do? To figure this out, you have to know about Sprite Groups.
Another super useful class that
pygame provides is the
Sprite Group. This is an object that holds a group of
Sprite objects. So why use it? Can’t you just track your
Sprite objects in a list instead? Well, you can, but the advantage of using a
Group lies in the methods it exposes. These methods help to detect whether any
Enemy has collided with the
Player, which makes updates much easier.
Let’s see how to create sprite groups. You’ll create two different
Groupwill hold every
Spritein the game.
Groupwill hold just the
Here’s what that looks like in code:
# Create the 'player' player = Player() # Create groups to hold enemy sprites and all sprites # - enemies is used for collision detection and position updates # - all_sprites is used for rendering enemies = pygame.sprite.Group() all_sprites = pygame.sprite.Group() all_sprites.add(player) # Variable to keep the main loop running running = True
When you call
Sprite is removed from every
Group to which it belongs. This removes the references to the
Sprite as well, which allows Python’s garbage collector to reclaim the memory as necessary.
Now that you have an
all_sprites group, you can change how objects are drawn. Instead of calling
.blit() on just
Player, you can iterate over everything in
# Fill the screen with black screen.fill((0, 0, 0)) # Draw all sprites for entity in all_sprites: screen.blit(entity.surf, entity.rect) # Flip everything to the display pygame.display.flip()
Now, anything put into
all_sprites will be drawn with every frame, whether it’s an enemy or the player.
There’s just one problem… You don’t have any enemies! You could create a bunch of enemies at the beginning of the game, but the game would quickly become boring when they all left the screen a few seconds later. Instead, let’s explore how to keep a steady supply of enemies coming as the game progresses.Custom Events
The design calls for enemies to appear at regular intervals. This means that at set intervals, you need to do two things:
You already have code that handles random events. The event loop is designed to look for random events occurring every frame and deal with them appropriately. Luckily,
pygame doesn’t restrict you to using only the event types it has defined. You can define your own events to handle as you see fit.
Let’s see how to create a custom event that’s generated every few seconds. You can create a custom event by naming it:
# Create the screen object # The size is determined by the constant SCREEN_WIDTH and SCREEN_HEIGHT screen = pygame.display.set_mode((SCREEN_WIDTH, SCREEN_HEIGHT)) # Create a custom event for adding a new enemy ADDENEMY = pygame.USEREVENT + 1 pygame.time.set_timer(ADDENEMY, 250) # Instantiate player. Right now, this is just a rectangle. player = Player()
pygame defines events internally as integers, so you need to define a new event with a unique integer. The last event
pygame reserves is called
USEREVENT, so defining
ADDENEMY = pygame.USEREVENT + 1 on line 83 ensures it’s unique.
Next, you need to insert this new event into the event queue at regular intervals throughout the game. That’s where the
time module comes in. Line 84 fires the new
ADDENEMY event every 250 milliseconds, or four times per second. You call
.set_timer() outside the game loop since you only need one timer, but it will fire throughout the entire game.
Add the code to handle your new event:
# Main loop while running: # Look at every event in the queue for event in pygame.event.get(): # Did the user hit a key? if event.type == KEYDOWN: # Was it the Escape key? If so, stop the loop. if event.key == K_ESCAPE: running = False # Did the user click the window close button? If so, stop the loop. elif event.type == QUIT: running = False # Add a new enemy? elif event.type == ADDENEMY: # Create the new enemy and add it to sprite groups new_enemy = Enemy() enemies.add(new_enemy) all_sprites.add(new_enemy) # Get the set of keys pressed and check for user input pressed_keys = pygame.key.get_pressed() player.update(pressed_keys) # Update enemy position enemies.update()
Whenever the event handler sees the new
ADDENEMY event on line 115, it creates an
Enemy and adds it to
allsprites. Since Enemy is in allsprites, it will get drawn every frame. You also need to call
enemies.update() on line 126, which updates everything in
enemies, to ensure they move properly:
However, that’s not the only reason there’s a group for just
Your game design calls for the game to end whenever an enemy collides with the player. Checking for collisions is a basic technique of game programming, and usually requires some non-trivial math to determine whether two sprites will overlap each other.
This is where a framework like
pygame comes in handy! Writing collision detection code is tedious, but
pygame has a LOT of collision detection methods available for you to use.
For this tutorial, you’ll use a method called
.spritecollideany(), which is read as “sprite collide any.” This method accepts a
Sprite and a
Group as parameters. It looks at every object in the
Group and checks if its
.rect intersects with the
.rect of the
Sprite. If so, then it returns
True. Otherwise, it returns
False. This is perfect for this game since you need to check if the single
player collides with one of a
Here’s what that looks like in code:
# Draw all sprites for entity in all_sprites: screen.blit(entity.surf, entity.rect) # Check if any enemies have collided with the player if pygame.sprite.spritecollideany(player, enemies): # If so, then remove the player and stop the loop player.kill() running = False
Line 135 tests whether
player has collided with any of the objects in
enemies. If so, then
player.kill() is called to remove it from every group to which it belongs. Since the only objects being rendered are in
player will no longer be rendered. Once the player has been killed, you need to exit the game as well, so you set
running = False to break out of the game loop on line 138.
At this point, you’ve got the basic elements of a game in place:
Now, let’s dress it up a bit, make it more playable, and add some advanced capabilities to help it stand out.Sprite Images
Alright, you have a game, but let’s be honest… It’s kind of ugly. The player and enemies are just white blocks on a black background. That was state-of-the-art when Pong was new, but it just doesn’t cut it anymore. Let’s replace all those boring white rectangles with some cooler images that will make the game feel like an actual game.
Earlier, you learned that images on disk can be loaded into a
Surface with some help from the
image module. For this tutorial, we made a little jet for the player and some missiles for the enemies. You’re welcome to use this art, draw your own, or download some free game art assets to use. You can click the link below to download the art used in this tutorial:
Clone Repo: Click here to clone the repo you'll use to learn how to use PyGame in this tutorial.
Before you use images to represent the player and enemy sprites, you need to make some changes to their constructors. The code below replaces the code used previously:
# Import pygame.locals for easier access to key coordinates # Updated to conform to flake8 and black standards # from pygame.locals import * from pygame.locals import ( RLEACCEL, K_UP, K_DOWN, K_LEFT, K_RIGHT, K_ESCAPE, KEYDOWN, QUIT, ) # Define constants for the screen width and height SCREEN_WIDTH = 800 SCREEN_HEIGHT = 600 # Define the Player object by extending pygame.sprite.Sprite # Instead of a surface, use an image for a better-looking sprite class Player(pygame.sprite.Sprite): def __init__(self): super(Player, self).__init__() self.image = pygame.image.load("jet.png").convert() self.image.set_colorkey((255, 255, 255), RLEACCEL) self.rect = self.image.get_rect()
Let’s unpack line 31 a bit.
pygame.image.load() loads an image from the disk. You pass it a path to the file. It returns a
Surface, and the
.convert() call optimizes the
Surface, making future
.blit() calls faster.
Line 32 uses
.set_colorkey() to indicate the color
pygame will render as transparent. In this case, you choose white, because that’s the background color of the jet image. The RLEACCEL constant is an optional parameter that helps
pygame render more quickly on non-accelerated displays. This is added to the
pygame.locals import statement on line 11.
Nothing else needs to change. The image is still a
Surface, except now it has a picture painted on it. You still use it in the same way.
Here’s what similar changes to the
Enemy look like:
# Define the enemy object by extending pygame.sprite.Sprite # Instead of a surface, use an image for a better-looking sprite class Enemy(pygame.sprite.Sprite): def __init__(self): super(Enemy, self).__init__() self.surf = pygame.image.load("missile.png").convert() self.surf.set_colorkey((255, 255, 255), RLEACCEL) # The starting position is randomly generated, as is the speed self.rect = self.surf.get_rect( center=( random.randint(SCREEN_WIDTH + 20, SCREEN_WIDTH + 100), random.randint(0, SCREEN_HEIGHT), ) ) self.speed = random.randint(5, 20)
Running the program now should show that this is the same game you had before, except now you’ve added some nice graphics skins with images. But why stop at just making the player and enemy sprites look nice? Let’s add a few clouds going past to give the impression of a jet flying through the sky.
For background clouds, you use the same principles as you did for
.update()that moves the
cloudtoward the left side of the screen.
cloudobjects at a set time interval.
cloudobjects to a new
cloudsin your game loop.
Cloud looks like:
# Define the cloud object by extending pygame.sprite.Sprite # Use an image for a better-looking sprite class Cloud(pygame.sprite.Sprite): def __init__(self): super(Cloud, self).__init__() self.surf = pygame.image.load("cloud.png").convert() self.surf.set_colorkey((0, 0, 0), RLEACCEL) # The starting position is randomly generated self.rect = self.surf.get_rect( center=( random.randint(SCREEN_WIDTH + 20, SCREEN_WIDTH + 100), random.randint(0, SCREEN_HEIGHT), ) # Move the cloud based on a constant speed # Remove the cloud when it passes the left edge of the screen def update(self): self.rect.move_ip(-5, 0) if self.rect.right < 0: self.kill()
That should all look very familiar. It’s pretty much the same as
To have clouds appear at certain intervals, you’ll use event creation code similar to what you used to create new enemies. Put it right below the enemy creation event:
# Create custom events for adding a new enemy and a cloud ADDENEMY = pygame.USEREVENT + 1 pygame.time.set_timer(ADDENEMY, 250) ADDCLOUD = pygame.USEREVENT + 2 pygame.time.set_timer(ADDCLOUD, 1000)
This says to wait 1000 milliseconds, or one second, before creating the next
Next, create a new
Group to hold each newly created
# Create groups to hold enemy sprites, cloud sprites, and all sprites # - enemies is used for collision detection and position updates # - clouds is used for position updates # - all_sprites is used for rendering enemies = pygame.sprite.Group() clouds = pygame.sprite.Group() all_sprites = pygame.sprite.Group() all_sprites.add(player)
Next, add a handler for the new
ADDCLOUD event in the event handler:
# Main loop while running: # Look at every event in the queue for event in pygame.event.get(): # Did the user hit a key? if event.type == KEYDOWN: # Was it the Escape key? If so, then stop the loop. if event.key == K_ESCAPE: running = False # Did the user click the window close button? If so, stop the loop. elif event.type == QUIT: running = False # Add a new enemy? elif event.type == ADDENEMY: # Create the new enemy and add it to sprite groups new_enemy = Enemy() enemies.add(new_enemy) all_sprites.add(new_enemy) # Add a new cloud? elif event.type == ADDCLOUD: # Create the new cloud and add it to sprite groups new_cloud = Cloud() clouds.add(new_cloud) all_sprites.add(new_cloud)
Finally, make sure the
clouds are updated every frame:
# Update the position of enemies and clouds enemies.update() clouds.update() # Fill the screen with sky blue screen.fill((135, 206, 250))
Line 172 updates the original
screen.fill() to fill the screen with a pleasant sky blue color. You can change this color to something else. Maybe you want an alien world with a purple sky, a toxic wasteland in neon green, or the surface of Mars in red!
Note that each new
Enemy are added to
all_sprites as well as
enemies. This is done because each group is used for a separate purpose:
You create multiple groups so that you can change the way sprites move or behave without impacting the movement or behavior of other sprites.Game Speed
While testing the game you may have noticed that the enemies move a little fast. If not, then that’s okay, as different machines will see different results at this point.
The reason for this is that the game loop processes frames as fast as the processor and environment will allow. Since all the sprites move once per frame, they can move hundreds of times each second. The number of frames handled each second is called the frame rate, and getting this right is the difference between a playable game and a forgettable one.
Normally, you want as high a frame rate as possible, but for this game, you need to slow it down a bit for the game to be playable. Fortunately, the module
time contains a
Clock which is designed exactly for this purpose.
Clock to establish a playable frame rate requires just two lines of code. The first creates a new
Clock before the game loop begins:
# Setup the clock for a decent framerate clock = pygame.time.Clock()
The second calls
.tick() to inform
pygame that the program has reached the end of the frame:
# Flip everything to the display pygame.display.flip() # Ensure program maintains a rate of 30 frames per second clock.tick(30)
The argument passed to
.tick() establishes the desired frame rate. To do this,
.tick() calculates the number of milliseconds each frame should take, based on the desired frame rate. Then, it compares that number to the number of milliseconds that have passed since the last time
.tick() was called. If not enough time has passed, then
.tick() delays processing to ensure that it never exceeds the specified frame rate.
Passing in a smaller frame rate will result in more time in each frame for calculations, while a larger frame rate provides smoother (and possibly faster) gameplay:
Play around with this number to see what feels best for you!Sound Effects
So far, you’ve focused on gameplay and the visual aspects of your game. Now let’s explore giving your game some auditory flavor as well.
mixer to handle all sound-related activities. You’ll use this module’s classes and methods to provide background music and sound effects for various actions.
mixer refers to the fact that the module mixes various sounds into a cohesive whole. Using the
music sub-module, you can stream individual sound files in a variety of formats, such as MP3, Ogg, and Mod. You can also use
Sound to hold a single sound effect to be played, in either Ogg or uncompressed WAV formats. All playback happens in the background, so when you play a
Sound, the method returns immediately as the sound plays.
pygame documentation states that MP3 support is limited, and unsupported formats can cause system crashes. The sounds referenced in this article have been tested, and we recommend testing any sounds thoroughly before releasing your game.
As with most things
mixer starts with an initialization step. Luckily, this is already handled by
pygame.init(). You only need to call
pygame.mixer.init() if you want to change the defaults:
# Setup for sounds. Defaults are good. pygame.mixer.init() # Initialize pygame pygame.init() # Set up the clock for a decent framerate clock = pygame.time.Clock()
pygame.mixer.init() accepts a number of arguments, but the defaults work fine in most cases. Note that if you want to change the defaults, you need to call
pygame.mixer.init() before calling
pygame.init(). Otherwise, the defaults will be in effect regardless of your changes.
After the system is initialized, you can get your sounds and background music setup:
# Load and play background music # Sound source: http://ccmixter.org/files/Apoxode/59262 # License: https://creativecommons.org/licenses/by/3.0/ pygame.mixer.music.load("Apoxode_-_Electric_1.mp3") pygame.mixer.music.play(loops=-1) # Load all sound files # Sound sources: Jon Fincher move_up_sound = pygame.mixer.Sound("Rising_putter.ogg") move_down_sound = pygame.mixer.Sound("Falling_putter.ogg") collision_sound = pygame.mixer.Sound("Collision.ogg")
Lines 138 and 139 load a background sound clip and begin playing it. You can tell the sound clip to loop and never end by setting the named parameter
Lines 143 to 145 load three sounds you’ll use for various sound effects. The first two are rising and falling sounds, which are played when the player moves up or down. The last is the sound used whenever there is a collision. You can add other sounds as well, such as a sound for whenever an
Enemy is created, or a final sound for when the game ends.
So, how do you use the sound effects? You want to play each sound when a certain event occurs. For example, when the ship moves up, you want to play
move_up_sound. Therefore, you add a call to
.play() whenever you handle that event. In the design, that means adding the following calls to
# Define the Player object by extending pygame.sprite.Sprite # Instead of a surface, use an image for a better-looking sprite class Player(pygame.sprite.Sprite): def __init__(self): super(Player, self).__init__() self.surf = pygame.image.load("jet.png").convert() self.surf.set_colorkey((255, 255, 255), RLEACCEL) self.rect = self.surf.get_rect() # Move the sprite based on keypresses def update(self, pressed_keys): if pressed_keys[K_UP]: self.rect.move_ip(0, -5) move_up_sound.play() if pressed_keys[K_DOWN]: self.rect.move_ip(0, 5) move_down_sound.play()
For a collision between the player and an enemy, you play the sound for when collisions are detected:
# Check if any enemies have collided with the player if pygame.sprite.spritecollideany(player, enemies): # If so, then remove the player player.kill() # Stop any moving sounds and play the collision sound move_up_sound.stop() move_down_sound.stop() collision_sound.play() # Stop the loop running = False
Here, you stop any other sound effects first, because in a collision the player is no longer moving. Then you play the collision sound and continue execution from there.
Finally, when the game is over, all sounds should stop. This is true whether the game ends due to a collision or the user exits manually. To do this, add the following lines at the end of the program after the loop:
# All done! Stop and quit the mixer. pygame.mixer.music.stop() pygame.mixer.quit()
Technically, these last few lines are not required, as the program ends right after this. However, if you decide later on to add an intro screen or an exit screen to your game, then there may be more code running after the game ends.
That’s it! Test it again, and you should see something like this:A Note on Sources
You may have noticed the comment on lines 136-137 when the background music was loaded, listing the source of the music and a link to the Creative Commons license. This was done because the creator of that sound required it. The license requirements stated that in order to use the sound, both proper attribution and a link to the license must be provided.
Here are some sources for music, sound, and art that you can search for useful content:
As you make your games and use downloaded content such as art, music, or code from other sources, please be sure that you are complying with the licensing terms of those sources.Conclusion
Throughout this tutorial, you’ve learned how game programming with
pygame differs from standard procedural programming. You’ve also learned how to:
To do this, you used a subset of the
pygame modules, including the
key modules. You also used several
pygame classes, including
Sprite. But these only scratch the surface of what
pygame can do! Check out the official
pygame documentation for a full list of available modules and classes.
You can find all of the code, graphics, and sound files for this article by clicking the link below:
Clone Repo: Click here to clone the repo you'll use to learn how to use PyGame in this tutorial.
Feel free to leave comments below as well. Happy Pythoning!
Thanks for reading ❤
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Originally published at https://realpython.com/
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