PyGame Resources with less green

Foreword

This was written by Serena Chen in Spring 2017. If anything is unclear or should be added or changed, feel free to reach out to me over email or slack.

Example application:

import pygame

if __name__ == "__main__":
    pygame.init()
    screen = pygame.display.set_mode((800, 600)) # window size, as a tuple
    pygame.display.set_caption('PyGame App!')

    # change this block of code to do what you want
    running = True
    while running:
        for event in pygame.event.get():
            if event.type == pygame.QUIT: # user presses the x-button
                running = False

        screen.fill((0,0,0)) # RGB tuple for black
        pygame.display.update()

    pygame.quit()

Pygame Events

• The above example application has this code to read in events

for event in pygame.event.get():
    if event.type == pygame.QUIT: # user presses the x-button
        running = False

• pygame.event.get() will get you an EventList, which you can just treat as a list of pygame Event
• Each event has a type, which is represented by a constant in pygame.

Pygame Event Types

The following bullets assume you have an Event called event

• pygame.QUIT
  • When the user presses the ‘x’ button
• pygame.KEYDOWN
  • When a user presses a keyboard key
  • event.key: the name of the key pressed.

    • If you want to see if a user pressed a certain key (such as the letter ‘a’), you can write:

        if event.key == pygame.K_a:
      

    • Here is a list of pygame key constants

  • event.unicode: gets you the actual character that was pressed
  • event.mod: state of keyboard modifiers (ex. shift, alt, ctrl, etc). Interpreting the number you get requires bitwise ands.
    • There is a list of constants that represent all the modifiers, under the list of key constants on this page

    • To check if, for example, ‘a’ and ‘ctrl’ are held down, use

        if (event.key == pygame.K_a) and (event.mod & pygame.KMOD_CTRL):
      

    • I won’t get into bitwise operations, but if you really want to know, here is a resource.
• pygame.KEYUP
  • When a user lets go of a keyboard key
  • event.KEY
  • event.mod
  • Those descriptions are the same as above
• pygame.MOUSEMOTION
  • When the user moves the mouse in the window
  • event.pos: The ending position of the mouse as a tuple, where (0, 0) is the top left corner of the screen
  • event.rel: Amount of pixels moved, as a tuple (dx, dy)
  • event.buttons: The mouse buttons that were held down. It is a tuple like (left, middle, right), where each element is 1 if it was held, and 0 otherwise
• pygame.MOUSEBUTTONUP and pygame.MOUSEBUTTONDOWN
  • Pressing and letting go of the mouse button
  • They have the same parameters
  • event.pos: The position of the mouse as a tuple, where (0, 0) is the top left corner of the screen
  • event.button: A number that corresponds to the button pressed
    • 1: left mouse button
    • 2: middle mouse button
    • 3: right mouse button
    • 4: scroll up
    • 5: scroll down
• There are lots of other pygame events, but they won’t be used as much (especially in SofDes).
• Official Pygame event documentation
• Pygame’s official input handling tutorial

Commonly used graphics functions:

All functions assume that you have defined:

• screen = pygame.display.set_mode((800, 600))
• color = (0,0,0) – color is an RGB tuple/list; each element is from 0-255

Representing a rectangle object:

• box = pygame.Rect(x, y, width, height)
  • x and y are the int coordinates (as pixels) of the top left coordinate
  • width and height are integers; width/height in pixels
  • Rectangle objects are used for the draw_rect function; they are also good for storing the dimensions of a bounding box.
  • Get the dimensions of a rectangle by using rect.x, rect.y, rect.width, rect.height

Drawing shapes:

• Line
  • pygame.draw.line(screen, color, start_pos, end_pos, width=1)
  • start_pos and end_pos are tuples like (x, y); they are the pixel coordinates
  • width is optional; it is the number of pixels thick the line should be
• Rectangle
  • pygame.draw.rect(screen, color, rect, width=0)
  • rect is a rectangle object; described above
  • width is optional; it is the number of pixels thick the line should be
• Ellipse
  • pygame.draw.ellipse(screen, color, rect, width=0)
  • rect is a rectangle object; described above
  • width is optional; it is the number of pixels thick the line should be
• Circle
  • pygame.draw.circle(screen, color, pos, radius, width=0)
  • pos is the center coordinate, as a tuples
  • radius is the radius in pixels
  • width is optional; it is the number of pixels thick the line should be
• Pygame draw documentation

On the blit function

• The following section will use screen.blit()
• This function is used for drawing images, text, and other things
• The official purpose of blit is to draw one Surface onto another
• A Surface is an object that represents some sort of image.
  • screen, images, and text are all types of Surface

How to put an image onto the screen:

x = 0, y = 0 # top left x and y
width = 100, height = 100 # desired image width and height

img = pygame.image.load('image.png')
scaled_img = pygame.transform.scale(img, (width, height))
screen.blit(scaled_img, (x, y))

Pygame documentation for transforming images. Most of the functions you will need are relatively straightforward.

How to put text on the screen

x = 0, y = 0 # top left x and y

font = pygame.font.SysFont("monospace", 15) #font name, font size
label = font.render("text", 1, color) # see below
screen.blit(label, (x, y))

• Creating a label, given a pygame font named font
  • font.render(text, antialias, color, background=None)
  • text is a string, like above
  • antialias: This is a 1 or 0. Simply, this will alter how pixel-y your text looks. Either option should be ok; feel free to play with this.
    • If you want to know more about aliasing, see this Wikipedia article and this Wikipedia article for information.
  • background is optional; you can specify a background color for the text
• If you don’t care what font you use, you can replace "monospace" above with pygame.font.get_default_font()
• To see the list of fonts available to you, you can run print(pygame.font.get_fonts()).
• You can also download a font as a file, and then use that by saying font = pygame.font.Font(filename, size) where size is the font size