Self: How to Program a Game in Python with Pygame

This updated guide examines Self: How to Program a Game in Python with Pygame and organizes the essential facts, background, and practical takeaways in clear American English.

Part 1

Installing Pygame

Download Pygame. Find it for your platform from http://www.pygame.org/download.shtml.
Run the installer.
Verify that the installation worked. Open a Python terminal. Type "import pygame." If you don't see any errors then Pygame was successfully installed.
```
importpygame
```

Part 2

Setting Up A Basic Window

Open a new file.
Import Pygame. Pygame is a library that provides access to graphics functions. If you want more information on how these functions work, you can look them up on the Pygame website. https://www.pygame.org/docs/
```
importpygamefrompygame.localsimport*
```
Set the window resolution. You'll be making a global variable for the screen resolution so that can be referenced in several parts of the game. It's also easy to find at the top of the file so it can be changed later. For advanced projects, putting this information in a separate file would be a better idea.
```
resolution=(400,300)
```
Define some colors. Colors in pygame are (RBGA which range in values between 0 and 255. The alpha value (A) is optional but the other colors (red, blue, and green are mandatory).
```
white=(255,255,255)black=(0,0,0)red=(255,0,0)
```
Initialize the screen. Use the resolution variable that was defined earlier.
```
screen=pygame.display.set_mode(resolution)
```
Make a game loop. Repeat certain actions in every frame of our game. Make a loop that will always repeat to cycle through all these actions.
```
whileTrue:
```
Color the screen.
```
screen.fill(white)
```
Display the screen. If you run the program, the screen will turn white and then the program will crash. This is because the operating system is sending events to the game and the game isn't doing anything with them. Once the game receives too many unhandled events, it will crash.
```
whileTrue:...pygame.display.flip()
```
Handle events. Get a list of all events that have occurred in each frame. You're only going to care about one event, the quit event. This occurs when the user closes the game window. This will also prevent our program from crashing due to too many events.
```
whileTrue:...foreventinpygame.event.get():ifevent.type==QUIT:pygame.quit()
```

Self: How to Program a Game in Python with Pygame � contextual image 1

Try it out! Here's what the code should look like now:

importpygamefrompygame.localsimport*resolution=(400,300)white=(255,255,255)black=(0,0,0)red=(255,0,0)screen=pygame.display.set_mode(resolution)whileTrue:screen.fill(white)pygame.display.flip()foreventinpygame.event.get():ifevent.type==QUIT:pygame.quit()

Part 3

Making a Game Object

Make a new class and constructor. Set all the properties of the object. You're also providing default values for all the properties.

classBall:def__init__(self,xPos=resolution[0]/2,yPos=resolution[1]/2,xVel=1,yVel=1,rad=15):self.x=xPosself.y=yPosself.dx=xVelself.dy=yVelself.radius=radself.type="ball"

Define how to draw the object. Use the properties that were defined in the constructor to draw the ball as a circle as well as to pass a surface into the function to draw the object on. The surface will be the screen object that was created using the resolution earlier.
```
defdraw(self,surface):pygame.draw.circle(surface,black,(self.x,self.y),self.radius)
```
Make an instance of the class as well as to tell the game loop to draw the ball in every loop.
```
ball=Ball()whileTrue:...ball.draw(screen)
```
Make the object move. Create a function that will update the position of the object. Call this function in every game loop.
```
classBall:...defupdate(self):self.x+=self.dxself.y+=self.dy
```
Limit the frame rate. The ball will move really fast because the game loop is running hundreds of times a second. Use Pygame's clock to limit the frame rate to 60 fps.
```
clock=pygame.time.Clock()whileTrue:...clock.tick(60)
```
Keep the ball on the screen. Add checks in the update function to reverse the ball's direction if it hits one of the screen edges.
```
classBall:...defupdate(self):...if(self.x<=0orself.x>=resolution[0]):self.dx*=-1if(self.y<=0orself.y>=resolution[1]):self.dy*=-1
```

Self: How to Program a Game in Python with Pygame � contextual image 2

Try it out! Here's what the code should look like now:

importpygamefrompygame.localsimport*resolution=(400,300)white=(255,255,255)black=(0,0,0)red=(255,0,0)screen=pygame.display.set_mode(resolution)classBall:def__init__(self,xPos=resolution[0]/2,yPos=resolution[1]/2,xVel=1,yVel=1,rad=15):self.x=xPosself.y=yPosself.dx=xVelself.dy=yVelself.radius=radself.type="ball"defdraw(self,surface):pygame.draw.circle(surface,black,(self.x,self.y),self.radius)defupdate(self):self.x+=self.dxself.y+=self.dyif(self.x<=0orself.x>=resolution[0]):self.dx*=-1if(self.y<=0orself.y>=resolution[1]):self.dy*=-1ball=Ball()clock=pygame.time.Clock()whileTrue:screen.fill(white)ball.draw(screen)ball.update()pygame.display.flip()clock.tick(60)foreventinpygame.event.get():ifevent.type==QUIT:pygame.quit()

Part 4

Organizing the Game

Use classes to organize everything. The game is going to get more complicated. Use object-oriented techniques to organize your code.
Make the game loop into a class. Since our game now has data including your game objects and functions, it makes sense to turn your game loop into a class.
```
classgame():
```
Add a constructor. Here you will instantiate some game objects, create our screen and clock and initialize Pygame. Pygame needs to be initialized to use certain features like text or sound.
```
classgame():def__init__(self):pygame.init()self.screen=pygame.display.set_mode(resolution)self.clock=pygame.time.Clock()
```

Handle events in a function.

classgame():...defhandleEvents(self):foreventinpygame.event.get():ifevent.type==QUIT:pygame.quit()

Make the game loop a function. Call the event handling function every loop.

classgame():...defrun(self):whileTrue:self.handleEvents()self.screen.fill(white)self.clock.tick(60)pygame.display.flip()

Handle multiple game objects. Right now this code has to call draw and update on our object each frame. This would get messy if you had a lot of objects. Let's add our object to an array and then update and draw all objects in the array every loop. Now you can easily add another object and give it a different starting position.
```
classgame():def__init__(self):...self.gameObjects=[]self.gameObjects.append(Ball())self.gameObjects.append(Ball(100))...defrun(self):whileTrue:self.handleEvents()forgameObjinself.gameObjects:gameObj.update()self.screen.fill(white)forgameObjinself.gameObjects:gameObj.draw(self.screen)self.clock.tick(60)pygame.display.flip()
```

Self: How to Program a Game in Python with Pygame � contextual image 3

Try it out! Here's what the code should look like now:

importpygamefrompygame.localsimport*resolution=(400,300)white=(255,255,255)black=(0,0,0)red=(255,0,0)screen=pygame.display.set_mode(resolution)classBall:def__init__(self,xPos=resolution[0]/2,yPos=resolution[1]/2,xVel=1,yVel=1,rad=15):self.x=xPosself.y=yPosself.dx=xVelself.dy=yVelself.radius=radself.type="ball"defdraw(self,surface):pygame.draw.circle(surface,black,(self.x,self.y),self.radius)defupdate(self):self.x+=self.dxself.y+=self.dyif(self.x<=0orself.x>=resolution[0]):self.dx*=-1if(self.y<=0orself.y>=resolution[1]):self.dy*=-1classgame():def__init__(self):pygame.init()self.screen=pygame.display.set_mode(resolution)self.clock=pygame.time.Clock()self.gameObjects=[]self.gameObjects.append(Ball())self.gameObjects.append(Ball(100))defhandleEvents(self):foreventinpygame.event.get():ifevent.type==QUIT:pygame.quit()defrun(self):whileTrue:self.handleEvents()forgameObjinself.gameObjects:gameObj.update()self.screen.fill(white)forgameObjinself.gameObjects:gameObj.draw(self.screen)self.clock.tick(60)pygame.display.flip()game().run()

Part 5

Adding a Player Object

Make a player class and constructor. You're going to make another circle that is controlled by the mouse. Initialize the values in the constructor. The radius is the only important value.
```
classPlayer:def__init__(self,rad=20):self.x=0self.y=0self.radius=rad
```
Define how to draw the player object. It's going to be the same way you drew the other game objects.
```
classPlayer:...defdraw(self,surface):pygame.draw.circle(surface,red,(self.x,self.y),self.radius)
```
Add mouse control for the player object. In every frame, check the location of the mouse and set the players' objects' location to that point.
```
classPlayer:...defupdate(self):cord=pygame.mouse.get_pos()self.x=cord[0]self.y=cord[1]
```
Add a player object to gameObjects. Create a new player instance and add it to the list.
```
classgame():def__init__(self):...self.gameObjects.append(Player())
```
Try it out! Here's what the code should look like

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