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Pygame Cookbook - Recipes for Mastering Pygame

Hi,

in the last years I used Python and the module Pygame to create some games. I found many information about Pygame on many different places in the web. I would prefer one book where I can look for solutions. So I started to write this Pygame Cookbook.

Pygame (https://www.pygame.org) is a create library for making your own games with python. Pygame uses the SDL library.

This Pygame Cookbook tries to explain the building blocks of a game simple and in detail.

The official documentation of Pygame is available at https://www.pygame.org/docs/.

If you like Pygame Cookbook, use it. If you have some suggestions, tell me ([email protected]).

All game assets that I use in recipes are from https://www.kenney.nl. Thank you.

Have fun.

Hebi, on the way to Python Ninja

Edition 0.32, July 2023

install pygame

Prerequisite for using the Pygame Cookbook is that the Python library Pygame is installed on your computer. $ pip install pygame More about installing pygame https://www.pygame.org/wiki/GettingStarted#Pygame%20Installation

You can use Pygame with different programming environments. A very convenient way to try the recipes of this Cookbook is to copy the Jupyter Notebook version (file pygame-cookbook.ipynb) to your computer and evaluate the cells your interested in.

pygame and jupyter notebooks

Task: Using pygame with Jupyter Notebooks

Solution:

Open a window that shows the drawing of pygame.

You can

%gui qt
import pygame
 
pygame.init() #start the pygame module

screen = pygame.display.set_mode((400, 300)) #get access to the display

pygame.display.update() #update the display
pygame 2.0.1 (SDL 2.0.14, Python 3.8.8)
Hello from the pygame community. https://www.pygame.org/contribute.html

Now you can use another jupyter cell to draw a rectangle.

pygame.draw.rect(screen, (0, 128, 255), pygame.Rect(30, 30, 60, 60)) #draw a rectangle

pygame.display.update() #update display

At least close the pygame window.

pygame.quit() #stop the pygame module












Explanation:

With the magic command%gui qt Jupyter can work together with Pygame. This enables the use of the Jupyter GUI and the entries in the Pygame window at the same time. Therefore every recipe in this Pygame Cookbook has the magic command%gui qt in the first line.

You don't need that, if you want to try a recipe in a different Python environment.

More:

https://ipython.readthedocs.io/en/stable/config/eventloops.html

simple gameloop

Task: simple program structure that works with every game

Solution:

Opens a window that shows the drawing of pygame.

%gui qt
import pygame

# ---- Initialize ----

pygame.init()

SIZE = WIDTH, HEIGHT = 320, 240
BLACK = 0, 0, 0
BLUE = 0, 0, 255

running = True
screen = pygame.display.set_mode(SIZE)

# ---- Game loop ----

while running:
    
    # ---- input ----
    for event in pygame.event.get():
        if event.type == pygame.QUIT: 
            running = False
    
    # ---- update ---- 
    
    # ---- draw ----
    screen.fill(BLACK)
    pygame.draw.rect(screen, BLUE, pygame.Rect(30, 30, 60, 60)) #draw a rectangle
    pygame.display.flip()

# ---- Quit ----

pygame.quit()











Explanation:

Every game consists of the same building blocks:

  • Input: Read input from player. Which keys are pressed? Did the mouse move? Any other input device lika a joystick?

  • Update: Do the changes in the game world

  • Draw: Show the changes on the screen

  • and start all over again

This is called game loop or event loop.

import pygame .. import the Pygame module
init() -> (numpass, numfail) .. initialize all imported Pygame modules. Some Pygame modules needs to be initialized. Return value numfail shows how many modules could not be initialized by Pygame.

pygame.display.set_mode() .. return a Surface object on which python can draw. The first parameters define the size. The created display will be the best supported by the system.

There are many additional flags:

pygame.FULLSCREEN .. fullscreen no window
pygame.HWSURFACE .. hardware accelerated (only fullscreen). pygame.OPENGL .. create an OpenGL-renderable display
pygame.RESIZABLE .. resizable window
pygame.NOFRAME .. window without border or controls

pygame.event.get(eventtype=None) -> Eventlist .. get next event from Pygame.
if event.type == pygame.QUIT: .. user clicked on the close control of the window.

screen.fill(BLACK) .. fill the complete display with color
pygame.draw.rect .. draw a rectangle on the display

pygame.display.flip() .. show changed display on the screen

pygame.quit() -> None .. uninitialize all imported Pygame modules

This loop will be used in the most recipes.

more

gameloop with timing

Task: integrating time into the game loop

Solution:

using class pygame.time.clock to get a good timing

%gui qt
import pygame

# ---- Initialize ----

pygame.init()

SIZE = WIDTH, HEIGHT = 320, 240
BLACK = 0, 0, 0
BLUE = 0, 0, 255

running = True
screen = pygame.display.set_mode(SIZE)

clock = pygame.time.Clock() #create clock object

FRAMES_PER_SECOND = 30      #who many pictures per second should pygame generate?

x_position = 60             #position of the blue rectangel
PIXELS_PER_SECOND = 40      #how many pixels per second should the rectangele be moved?

# ---- Game loop ----

while running:
    
    # ---- input ----
    for event in pygame.event.get():
        if event.type == pygame.QUIT: 
            running = False
    
    # ---- update ---- 
    delta_time = clock.tick(FRAMES_PER_SECOND)     # time since last frame
    
    x_position = x_position + delta_time/1000 * PIXELS_PER_SECOND #next position of the rectanel
 
    if x_position > WIDTH: #rectangele vanishes right start from left again
        x_position = 0
    
    # ---- draw ----
    screen.fill(BLACK)
    pygame.draw.rect(screen, BLUE, pygame.Rect(int(x_position), 30, 60, 60)) #draw a rectangle
    pygame.display.flip()

# ---- Quit ----

pygame.quit()

Explanation:

Pygame comes with an integrated class for timing: pygame.time.Clock

-Initialize-

First you have to create your own clock object.

clock = pygame.time.Clock()

FRAMES_PER_SECOND = 30 .. you have to define how many frames (pictures) should be maximal drawn by Pygame in a second

x_position = 60 .. the blue rectangle will move from left to right. In every frame the script will use the time since the last frame to calculate the new position.

PIXELS_PER_SECOND = 40 .. the speed (velocity) of the rectangle will be 40 pixels in one second.

-Game loop update()-

delta_time = clock.tick(FRAMES_PER_SECOND) .. returns the milliseconds since the last frame.
The parameter FRAMES_PER_SECOND defines the maximal number of frames per second. It limits the runtime. Pygame will not draw more frames per second.

x_position = x_position + delta_time/1000 * PIXELS_PER_SECOND .. to get the distance covered since the last frame you have to multiply the elapsed time by the velocity. delta_time is in milliseconds but you need the time in seconds. So you have to divide with thousand.

if x_position > WIDTH: x_position = 0.. before the rectangel is vanishing from the screen you have to start from the left side again

basics

coordinates

colors

Rect











draw

rectangle

Task: drawing a rectangle

Solution:

%gui qt
import pygame

pygame.init()

SIZE = WIDTH, HEIGHT = 320, 240
running = True
screen = pygame.display.set_mode(SIZE)

while running:
    
    for event in pygame.event.get():
        if event.type == pygame.QUIT: 
            running = False
            
    screen.fill(pygame.Color('black'))
    pygame.draw.rect(screen, pygame.Color('blue'), pygame.Rect(30, 30, 60, 60))
    pygame.display.flip()

pygame.quit()
%gui qt
import pygame

# ---- Initialize ----

pygame.init()

SIZE = WIDTH, HEIGHT = 320, 120

running = True
screen = pygame.display.set_mode(SIZE)

# ---- Game loop ----

while running:
    
    # ---- input ----
    for event in pygame.event.get():
        if event.type == pygame.QUIT: 
            running = False
    
    # ---- update ---- 
    
    # ---- draw ----
    screen.fill(BLACK)
    
    pygame.draw.rect(screen, pygame.Color('blue'), pygame.Rect(30, 30, 60, 60)) #fill area
    
    pygame.draw.rect(screen, pygame.Color('blue'), pygame.Rect(120, 30, 60, 60), width=1) #border
    
    pygame.draw.rect(screen, pygame.Color('blue'), pygame.Rect(210, 30, 60, 60), width=2, border_radius=8) #rounded border
    
    pygame.display.flip()

# ---- Quit ----

pygame.quit()











Explanation:

A rectangle can consist of a fill area and a border.

Drawing the fill area with function rect

rect(surface, color, rect) -> Rec .. draws a rectangle to the output surface and returns an object of the class Rect

surface.. Surface to draw on

color .. different ways to describe a color in Pygame

rec .. rectangle that describes position, width and height

With

Rect(left, top, width, height) -> Rect .. you can create a new Rect from position (left, top) and dimension (width, height)

Drawing the border with function rect

rect(surface, color, rect, width=0, border_radius=0) -> Rect .. draws the border of a rectangle to the output surface and returns an object of the class Rect

width.. thickness of the border in Pixel. (if is 0, Pygame draws a filled rectangle)

border_radius.. draws border with rounded corners (if is 0, no rounded corners)

more

polygon, circle, ellipse, arc

line

image

text

Task: draw text

Solution:

%gui qt
import pygame

running = True

WHITE = (255,255,255)
BLUE = (0,0,255)

pygame.init()
screen = pygame.display.set_mode((640, 340))

sysfont = pygame.font.get_default_font()
print(sysfont)

font = pygame.font.SysFont(None, 24)

pygame.display.flip()

while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT: 
            running = False
    
    screen.fill(WHITE)
    
    img = font.render("text", True, BLUE)
    rect = img.get_rect()
    rect.midtop = (40,40)
    screen.blit(img, rect)
    
    pygame.display.flip()
            
pygame.quit()
pygame 2.1.2 (SDL 2.0.18, Python 3.9.16)
Hello from the pygame community. https://www.pygame.org/contribute.html
freesansbold.ttf

Explanation:

get_default_font() -> str .. returns the name of the default font

SysFont(name, size) -> Font .. create a Font object from the system fonts

name.. name of the font, can be None

size.. font size

Font(filename, size) -> Font.. create Font from file

filename.. file name of the font

size.. font size

render(text, antialias, color, background=None) -> Surface .. creates a new surface with text

text.. as string
antialias.. if True than with antialias

The text can only be a single line. The Surface will be of the dimensions required to hold the text.

transparent

Task: draw a transparent surface

Solution:

%gui qt
import pygame

# ---- Initialize ----

pygame.init()

SIZE = WIDTH, HEIGHT = 640, 340

running = True
screen = pygame.display.set_mode(SIZE)

WHITE = (255,255,255)
BLUE = (0,0,255)
GREY_1 = (160, 160, 160)
GREY_2 = (192, 192, 192)

TILE_SIZE = 24
background = pygame.Surface(SIZE) # background image

for x in range(0,WIDTH//TILE_SIZE+1):
    for y in range(0,HEIGHT//TILE_SIZE+1):
        color = GREY_1
        if (x+y) % 2 == 0:
            color = GREY_2
        pygame.draw.rect(background, color, (x*TILE_SIZE, y*TILE_SIZE, TILE_SIZE, TILE_SIZE))

# ---- Game loop ----

while running:
    
    # ---- input ----
    for event in pygame.event.get():
        if event.type == pygame.QUIT: 
            running = False
    
    # ---- update ---- 
    
    # ---- draw ----
    screen.blit(background, (0, 0))
    
    surface = pygame.Surface((200,200))  # new surface
    surface.set_alpha(128)               # set alpha
    surface.fill(BLUE)             
    
    screen.blit(surface, (0,0))
    
    pygame.display.flip()

# ---- Quit ----

pygame.quit()
---------------------------------------------------------------------------

KeyboardInterrupt                         Traceback (most recent call last)

Cell In[5], line 48
     44     surface.fill(BLUE)             
     46     screen.blit(surface, (0,0))
---> 48     pygame.display.flip()
     50 # ---- Quit ----
     52 pygame.quit()


KeyboardInterrupt: 

If you want a transparent image (surface) you have to that the so called alpha value of the surface. Use the set_alpha method for this.

If the alpha value is 0 it's totaly transparent. You see nothing. If the value is 255 it's not transpartent.

set_alpha(value) -> None .. set alpha value of surface











Task: make every pixel of an image transparent

Solution:

%gui qt
import pygame

# ---- Initialize ----

pygame.init()

SIZE = WIDTH, HEIGHT = 320, 140

running = True
screen = pygame.display.set_mode(SIZE)

WHITE = (255,255,255)
BLUE = (0,0,255)
GREY_1 = (160, 160, 160)
GREY_2 = (192, 192, 192)

TILE_SIZE = 24
background = pygame.Surface(SIZE) # background image

for x in range(0,WIDTH//TILE_SIZE+1):
    for y in range(0,HEIGHT//TILE_SIZE+1):
        color = GREY_1
        if (x+y) % 2 == 0:
            color = GREY_2
        pygame.draw.rect(background, color, (x*TILE_SIZE, y*TILE_SIZE, TILE_SIZE, TILE_SIZE))

# ---- Game loop ----

while running:
    
    # ---- input ----
    for event in pygame.event.get():
        if event.type == pygame.QUIT: 
            running = False
    
    # ---- update ---- 
    
    # ---- draw ----
    screen.blit(background, (0, 0))
    
    RADIUS = 50
    
    surface = pygame.Surface((100,100),pygame.SRCALPHA)  # new surface per pixel alpha
    pygame.draw.circle(surface, (0,0,255,128), (RADIUS, RADIUS), RADIUS) # with alpha
    screen.blit(surface,(0,0))
    
    surface = pygame.Surface((100,100),pygame.SRCALPHA)  # new surface per pixel alpha
    pygame.draw.circle(surface, (0,0,255,64), (RADIUS, RADIUS), RADIUS) # with alpha
    screen.blit(surface,(75,0))
    
    pygame.display.flip()

# ---- Quit ----

pygame.quit()

surface = pygame.Surface((100,100),pygame.SRCALPHA)

If you want to set an alpha value (transparence) separatly for every pixel to have to use pygame.SRCALPHA when creating a surface. Now pygame knows that you wants to use alpha values.

pygame.draw.circle(surface, (0,0,255,128), (RADIUS, RADIUS), RADIUS)

In the color value you can now add the alpha value (128), too.











more

mouse

Task: drag with the mouse

Solution:

%gui qt
import pygame

# ---- Initialize ----

pygame.init()

SIZE = WIDTH, HEIGHT = 320, 240
BLACK = 0, 0, 0
BLUE = 0, 0, 255

running = True
screen = pygame.display.set_mode(SIZE)

rectangle = pygame.rect.Rect(176, 134, 80, 80)
draging = False

pygame.mouse.set_visible(True)

# ---- Game loop ----

while running:
    
    # ---- input ----
    for event in pygame.event.get():
        if event.type == pygame.QUIT: 
            running = False
            
        elif event.type == pygame.MOUSEBUTTONDOWN:           
            if rectangle.collidepoint(event.pos):
                draging = True
                mouse_x, mouse_y = event.pos
                offset_x = rectangle.x - mouse_x
                offset_y = rectangle.y - mouse_y

        elif event.type == pygame.MOUSEBUTTONUP:          
            draging = False

        elif event.type == pygame.MOUSEMOTION:
            if draging:
                mouse_x, mouse_y = event.pos
                rectangle.x = mouse_x + offset_x
                rectangle.y = mouse_y + offset_y
    
    # ---- update ---- 
    
    # ---- draw ----
    screen.fill(BLACK)
    pygame.draw.rect(screen, BLUE, rectangle) #draw a rectangle
    pygame.display.flip()

# ---- Quit ----

pygame.quit()

keyboard

Task: get every pressed key

Solution:

%gui qt
import pygame

running = True

WHITE = (255,255,255)
BLUE = (0,0,255)
GREEN = (0,255,0)

screen = pygame.display.set_mode((640, 340))

rectangle = pygame.rect.Rect(200, 150, 40, 40)
rect_color = BLUE

while running:

    right_color = GREEN
    left_color = GREEN
    up_color = GREEN
    down_color = GREEN
    
    for event in pygame.event.get():
        if event.type == pygame.QUIT: 
            running = False
            
    keys=pygame.key.get_pressed()
    
    if keys[pygame.K_RIGHT]:
        right_color = BLUE
        
    if keys[pygame.K_LEFT]:
        left_color = BLUE
        
    if keys[pygame.K_UP]:
        up_color = BLUE
        
    if keys[pygame.K_DOWN]:
        down_color = BLUE
    
    screen.fill(WHITE)
    
    pygame.draw.rect(screen, right_color, (200, 100, 100, 100))
    pygame.draw.rect(screen, left_color, (0, 100, 100, 100))
    pygame.draw.rect(screen, up_color, (100, 0, 100, 100))
    pygame.draw.rect(screen, down_color, (100, 200, 100, 100))
    
    pygame.display.flip()

pygame.quit()
pygame 2.1.2 (SDL 2.0.18, Python 3.9.16)
Hello from the pygame community. https://www.pygame.org/contribute.html

get_pressed() -> bools .. get a boolean value for every key on the keybaord. Is True if key is pressed.

events

collision

point - rectangle

Task: detecting a point in a rectangle

Solution:

%gui qt
import pygame

# ---- Initialize ----

pygame.init()

SIZE = WIDTH, HEIGHT = 320, 240
WHITE =  255, 255 ,255
BLUE = 0, 0, 255
GREEN = 0, 255, 0

running = True
screen = pygame.display.set_mode(SIZE)

rectangle = pygame.rect.Rect(50, 50, 100, 100)
rect_color = BLUE

# ---- Game loop ----

while running:
    
    # ---- input ----
    for event in pygame.event.get():
        if event.type == pygame.QUIT: 
            running = False
        elif event.type == pygame.MOUSEMOTION:           
            if rectangle.collidepoint(event.pos):
                rect_color = GREEN
            else:         
                rect_color = BLUE
    
    # ---- update ---- 

    # ---- draw ----
    screen.fill(WHITE)
    pygame.draw.rect(screen, rect_color, rectangle)
    pygame.display.flip()

# ---- Quit ----

pygame.quit()

Explanation:

rect.collidepoint((x,y)) -> bool returns True if point is within rect

more

rectangle - rectangle

rect.colliderect(Rect) -> bool returns True if rectangles overlap
rect.collidelist(list) -> index returns index of the first rectangle that overlaps; -1 if nothing is found rect.collidelistall(list) -> indices returns indexes of all rectangles that overlap

rectangle - line

Task: detecting a line in a rectangle

%gui qt
import pygame

# ---- Initialize ----

pygame.init()

SIZE = WIDTH, HEIGHT = 320, 240
WHITE = 255, 255, 255
BLACK = 0, 0, 0
BLUE = 0, 0, 255
GRAY = 127, 127, 127
GREEN = 0, 255, 0

running = True
screen = pygame.display.set_mode(SIZE)

clock = pygame.time.Clock() #create clock object

FRAMES_PER_SECOND = 30      #who many pictures per second should pygame generate?

x_position = 60             #position of the blue rectangel
PIXELS_PER_SECOND = 40      #how many pixels per second should the rectangele be moved?

start_pos = (120,0)
end_pos = (120,200)

# ---- Game loop ----

while running:
    
    # ---- input ----
    for event in pygame.event.get():
        if event.type == pygame.QUIT: 
            running = False
    
    # ---- update ---- 
    delta_time = clock.tick(FRAMES_PER_SECOND)     # time since last frame
    
    x_position = x_position + delta_time/1000 * PIXELS_PER_SECOND #next position of the rectanel
 
    if x_position > WIDTH: #rectangele vanishes right start from left again
        x_position = 0
    
    # ---- draw ----
    screen.fill(BLACK)
    rect = pygame.Rect(int(x_position), 30, 60, 60)
    
    clip = rect.clipline(start_pos,end_pos)
    
    if len(clip) > 0:
        pygame.draw.rect(screen, GRAY, rect)
        pygame.draw.line(screen, WHITE, start_pos, end_pos, width=1)
        pygame.draw.line(screen, GREEN, clip[0], clip[1])
    else:
        pygame.draw.rect(screen, BLUE, rect)
        pygame.draw.line(screen, WHITE, start_pos, end_pos, width=1)
    
    
    pygame.display.flip()

# ---- Quit ----

pygame.quit()
pygame 2.1.1 (SDL 2.0.18, Python 3.9.7)
Hello from the pygame community. https://www.pygame.org/contribute.html

clipline(x1, y1, x2, y2) -> ((cx1, cy1), (cx2, cy2)) .. returns the coordinates of a line that in rectangle; an empty tuble when line complete out rectangle

pixel - pixel

%gui qt
import pygame
pygame.init()

SIZE = WIDTH, HEIGHT = 320, 240
BLACK = 0, 0, 0

running = True
clock = pygame.time.Clock()
fps = 30
screen = pygame.display.set_mode(SIZE)

ball = pygame.image.load("Freddy.png")
ballrect = ball.get_rect()
ballrect.center = (200,100)
ballmask = pygame.mask.from_surface(ball)


ball2 = pygame.image.load("Freddy.png")
ballrect2 = ball2.get_rect()
ballmask2 = pygame.mask.from_surface(ball2)

position = pygame.Vector2(100, 100)
velocity = pygame.Vector2(10,0)

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

    delta_time = clock.tick(fps) / 1000.0
    position = position + velocity * delta_time
    ballrect2.center = position
    
    offset_x = ballrect2.left - ballrect.left
    offset_y = ballrect2.top - ballrect.top
    
    if ballmask.overlap(ballmask2, (offset_x, offset_y)) != None:
        print('collision')
        
    screen.fill(BLACK)
    screen.blit(ball, ballrect)
    screen.blit(ball2, ballrect2)
    pygame.display.flip()

pygame.quit()
pygame.quit()

from_surface(Surface) -> Mask.. Creates a Mask object from the Surface by setting all the opaque pixels and not setting the transparent pixels
overlap(othermask, offset) -> (x, y).. Returns the first point of intersection encountered between this mask and othermask. None if there is no overlaping. offset is the distance between the two masks.

sprite - sprite

more

opengl

start

Task: using OpenGl with pygame

Solution:

install Python packages numpy,PyOpenGL and PyOpenGL_accelerate

pip install numpy PyOpenGL PyOpenGL_accelerate

%gui qt
import pygame

from OpenGL.GL import *
from OpenGL.GLU import *

verticies = ((1, -1, -1),(1, 1, -1),(-1, 1, -1),(-1, -1, -1),
             (1, -1, 1),(1, 1, 1),(-1, -1, 1),(-1, 1, 1))

edges = ((0,1),(0,3),(0,4),(2,1),
         (2,3),(2,7),(6,3),(6,4),
         (6,7),(5,1),(5,4),(5,7))

# ---- Initialize ----

pygame.init()

SIZE = WIDTH, HEIGHT = 640, 480
BLACK = 0, 0, 0
BLUE = 0, 0, 255

#pygame.display.gl_set_attribute(pygame.GL_MULTISAMPLEBUFFERS,1) #antialiasing
#pygame.display.gl_set_attribute(pygame.GL_MULTISAMPLESAMPLES,4)

#pygame.display.gl_set_attribute(pygame.GL_CONTEXT_PROFILE_MASK, #compatibility
#                                pygame.GL_CONTEXT_PROFILE_CORE)

running = True
screen = pygame.display.set_mode(SIZE,pygame.DOUBLEBUF | pygame.OPENGL)

gluPerspective(45, (WIDTH/HEIGHT), 0.1, 50)
glTranslatef(0.0,0.0,-5)

# ---- Game loop ----

while running:
    
    # ---- input ----
    for event in pygame.event.get():
        if event.type == pygame.QUIT: 
            running = False
    
    # ---- update ---- 
    
    # ---- draw ----
    glRotatef(1, 3, 1, 1)
    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT)
    
    glBegin(GL_LINES)
    for edge in edges:
        for vertex in edge:
            glVertex3fv(verticies[vertex])
    glEnd()
    
    pygame.display.flip()
    pygame.time.wait(10)

# ---- Quit ----

pygame.quit()

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Pygame Cookbook- Writing Games with Python

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