Running a simple game (Simple)

We will create a simple game that we will improve on further in the book. As is traditional in books about programming, we will start with a Hello World! example. It's not a game per se. It's important to notice the so-called main game loop where all the action happens and the usage of the Font module to render text. In this program we will manipulate a Pygame's Surface object, that is used for drawing and we will handle a quit event.

How to do it...

  1. Imports: First we will import the required Pygame modules. If Pygame is installed properly, we should get no errors, otherwise please return to the Preparing your development environment (Simple) recipe:
    import pygame, sys
from pygame.locals import *
  2. Initialization: We will initialize Pygame by creating a display of 400 by 300 pixels and setting the window title to Hello world:
    pygame.init()
screen = pygame.display.set_mode((400, 300))

pygame.display.set_caption('Hello World!')
  3. The main game loop: Games usually have a game loop, which runs forever until, for instance, a quit event occurs. In this example, we will only set a label with the text Hello world at coordinates (100, 100). The text has a font size of 19, red color, and falls back to the default font:
    while True: 
   sys_font = pygame.font.SysFont("None", 19)
   rendered = sys_font.render('Hello World', 0, (255, 100, 100))
   screen.blit(rendered, (100, 100))

   for event in pygame.event.get():
      if event.type == QUIT:
         pygame.quit()
         sys.exit()

   pygame.display.update()

    We get the following screenshot as the end result:

    How to do it...

    The following is the complete code for the Hello World example:

    import pygame, sys
from pygame.locals import *

pygame.init()
screen = pygame.display.set_mode((400, 300))

pygame.display.set_caption('Hello World!')

while True: 
   sysFont = pygame.font.SysFont("None", 19)
   rendered = sysFont.render('Hello World', 0, (255, 100, 100))
   screen.blit(rendered, (100, 100))
   for event in pygame.event.get():
      if event.type == QUIT:
         pygame.quit()
         sys.exit()

   pygame.display.update()

How it works...

It might not seem like much, but we learned a lot in this recipe. The functions that passed the review are summarized in the following table:

Function

Description

pygame.init()

This function performs the initialization and needs to be called before any other Pygame functions are called.

pygame.display.set_mode((400, 300))

This function creates a so-called Surface object to draw on. We give this function a tuple representing the width and height of the surface.

pygame.display.set_caption('Hello World!')

This function sets the window title to a specified string value.

pygame.font.SysFont("None", 19)

This function creates a system font from a comma-separated list of fonts (in this case none) and a font size parameter.

sysFont.render('Hello World', 0, (255, 100, 100))

This function draws text on a surface. The second parameter indicates whether anti-aliasing is used. The last parameter is a tuple representing the RGB values of a color.

screen.blit(rendered, (100, 100))

This function draws on a surface.

pygame.event.get()

This function gets a list of Event objects. Events represent some special occurrence in the system, such as a user quitting the game.

pygame.quit()

This function cleans up resources used by Pygame. Call this function before exiting the game.

pygame.display.update()

This function refreshes the surface.

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