AP CSP | PyGame

Pygame Basics

A basic Pygame application typically follows a structured format. It begins with importing the pygame module and initializing it to set up the library. Next, a game window is created and its dimensions specified. A game loop is then established, which continuously runs until the user decides to quit.

Key Points:

pygame.init(): Initializes all Pygame modules.
pygame.display.set_mode(): Creates a display surface.
pygame.display.set_caption(): Sets the title of the window.
while loop: Used to keep the window open until the user closes it.
pygame.event.get(): Checks for events, such as the user clicking the close button.
pygame.display.flip(): Updates the display.
pygame.quit(): Quits Pygame.

## PYGAME BASICS EXAMPLE ##
import pygame

pygame.init()

SCREEN_WIDTH, SCREEN_HEIGHT = SCREEN_SIZE =  800, 600
screen = pygame.display.set_mode(SCREEN_SIZE)   
pygame.display.set_caption("Pygame Basics")

running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
    pygame.display.flip()

pygame.quit()

Note: Pygame is not a built-in module for python. If you don't have the Pygame module installed yet on your computer, use the following command in a terminal.

python -m pip install pygame

Drawing Shapes

Pygame provides a versatile toolkit for drawing various shapes on the screen. To render a shape, you'll need to specify the target surface and the desired color. Additionally, each shape function requires specific parameters to define its geometry and appearance.

Basic Python Shapes:

Rectangle

pygame.draw.rect(surface, color, rect, width=0)

surface: The surface to draw on.
color: The color of the rectangle.
rect: A tuple representing the rectangle's position and dimensions (x, y, width, height).
width: Optional width of the rectangle's border. If 0, the rectangle is filled.

import pygame

pygame.init()
screen = pygame.display.set_mode((400,400))   

running = True
while running:
	for event in pygame.event.get():
		if event.type == pygame.QUIT:
			running = False
	pygame.draw.rect(screen, (255,0,0), (200,200,20,40), width=0)
	pygame.display.flip()

pygame.quit()

Circle

pygame.draw.circle(surface, color, center, radius, width=0)

surface: The surface to draw on.
color: The color of the circle.
center: A tuple representing the circle's center coordinates (x, y).
radius: The radius of the circle.
width: Optional width of the circle's border. If 0, the circle is filled.

import pygame

pygame.init()
screen = pygame.display.set_mode((400,400))   

running = True
while running:
	for event in pygame.event.get():
		if event.type == pygame.QUIT:
			running = False
	pygame.draw.circle(screen, (255,0,0), (200,200), 25, width=0)
	pygame.display.flip()

pygame.quit()

Line

pygame.draw.line(surface, color, start_pos, end_pos, width=1)

surface: The surface to draw on.
color: The color of the line.
start_pos: A tuple representing the starting point of the line.
end_pos: A tuple representing the ending point of the line.
width: The width of the line.

import pygame

pygame.init()
screen = pygame.display.set_mode((400,400))   

running = True
while running:
	for event in pygame.event.get():
		if event.type == pygame.QUIT:
			running = False
	pygame.draw.line(screen, (255,0,0), (0,0), (200,200), width=5)
	pygame.display.flip()

pygame.quit()

Polygon

pygame.draw.polygon(surface, color, points, width=0)

surface: The surface to draw on.
color: The color of the polygon.
points: A list of tuples representing the polygon's vertices.
width: Optional width of the polygon's border. If 0, the polygon is filled.

import pygame

pygame.init()
screen = pygame.display.set_mode((400,400))   

running = True
while running:
	for event in pygame.event.get():
		if event.type == pygame.QUIT:
			running = False
	pygame.draw.polygon(screen, (0,0,255), [(0,0),(200,100),(200,300),(0,400)], width=0)
	pygame.display.flip()

pygame.quit()

Using Images

Images are the lifeblood of most Pygame games. They provide the visual elements that make games engaging and immersive. Without images, games would be limited to text-based interfaces, significantly reducing their appeal.

Key Points:

Sprites: These are individual images representing characters, objects, or enemies in a game.
Backgrounds: These images form the backdrop of the game world.
UI Elements: Images can be used to create buttons, menus, health bars, and other interactive elements.
Particle Effects: Small images can be used to create dynamic effects like explosions, smoke, or rain.

How to use images:

Load Image

img = pygame.image.load("image.png")

Resize Image

img = pygame.transform.scale(img, (new_width , new_height))

Blit Image to Screen

screen.blit(img, (x_pos, y_pos))

## IMAGE EXAMPLE ##\
import pygame, random

x_pos = random.randint(0,263)
y_pos = random.randint(0,368)
delta_x = .02
delta_y = .02
pygame.init()

screen = pygame.display.set_mode((400,400))   
img = pygame.image.load("ap-csp-logo.png").convert()
img = pygame.transform.scale(img, (137 , 32))

running = True
while running:
	for event in pygame.event.get():
		if event.type == pygame.QUIT:
			running = False
	
	x_pos += delta_x
	y_pos += delta_y
	
	if x_pos < 0 or x_pos > 263:
		delta_x *= -1
	if y_pos < 0 or y_pos > 368:
		delta_y *= -1
		
	screen.fill((0, 0, 0))
	screen.blit(img, (x_pos, y_pos))
	pygame.display.flip()

pygame.quit()

Event Handling

Event handling is a crucial mechanism that allows your game to respond to user input and system events. It's like a listener, constantly monitoring for actions like key presses, mouse clicks, or window closures.

Common Event Types:

pygame.QUIT: Indicates the user has closed the window.
pygame.KEYDOWN and pygame.KEYUP: Represent key presses and releases, respectively. Attributes include key (the key code), mod (modifiers like shift or control), and unicode (the character associated with the key).
pygame.MOUSEBUTTONDOWN and pygame.MOUSEBUTTONUP: Represent mouse button presses and releases. Attributes include button (the button number), pos (the mouse position), and rel (the relative movement of the mouse).
pygame.MOUSEMOTION: Represents mouse movement. Attributes include pos (the new mouse position), rel (the relative movement), and buttons (a tuple indicating which mouse buttons are pressed)

## EVENT HANDLING EXAMPLE ##
import pygame, random

circ_pos_x, circ_pos_y = circ_pos = 200, 200
circ_color = (255, 255, 255)

pygame.init()

screen = pygame.display.set_mode((400,400))   

running = True
while running:
	for event in pygame.event.get():
		if event.type == pygame.QUIT:
			running = False
		elif event.type == pygame.MOUSEMOTION:
			circ_pos_x, circ_pos_y = event.pos[0], event.pos[1]
		elif event.type == pygame.MOUSEBUTTONUP:
			circ_color = (random.randint(0,255), random.randint(0,255), random.randint(0,255))
	
	keys_pressed = pygame.key.get_pressed()
	if keys_pressed[pygame.K_UP]:
		circ_pos_y -= .1
	if keys_pressed[pygame.K_DOWN]:
		circ_pos_y += .1
	if keys_pressed[pygame.K_LEFT]:
		circ_pos_x -= .1
	if keys_pressed[pygame.K_RIGHT]:
		circ_pos_x += .1
	
	if(circ_pos_x < 0):
		circ_pos_x = 0
	elif(circ_pos_x > 400):
		circ_pos_x = 400
	if(circ_pos_y < 0):
		circ_pos_y = 0
	elif(circ_pos_y > 400):
		circ_pos_y = 400
	circ_pos = circ_pos_x, circ_pos_y	
	
	screen.fill('black')
	pygame.draw.circle(screen, circ_color, tuple(circ_pos), 25, width=0)
	pygame.display.flip()

pygame.quit()

Note: The pygame.key.get_pressed() gets all keys currently being held down. This allows for adding movement continuously.