3. game file

3.1. Simple Game loop

The game loop has been organised in the Game class.

The Game class is first called using game = Game() in the __main__.py file

game = Game() calls the __init__ method which initializes pygame, sets up the screen size, sets the frame per second and set up the clock.

The simple game loop is called by game.run().
It has a while True loop.
It carries out 3 methods: check_event, draw, update.

check_event checks for user interaction, including mosue and keyboard.

In the starter code below it handles 3 ways to close the python program.

draw prepares any objects such as rects and sprites to be drawn to the screen.

In the starter code below it prepares to fills the screen surface with a solid colour.

update is for updating the screen and the clock.

In the starter code below it updates the screen and updates the clock.

import sys

import pygame as pg


class Game:
    def __init__(self):
        pg.init()
        self.WINDOW_WIDTH = 1200
        self.WINDOW_HEIGHT = 800
        self.FPS = 60
        self.screen = pg.display.set_mode((self.WINDOW_WIDTH, self.WINDOW_HEIGHT))
        pg.display.set_caption("My Game")
        self.clock = pg.time.Clock()
        self.running = False

    def check_event(self):
        for event in pg.event.get():
            if event.type == pg.QUIT:
                self.run = False
            elif event.type == pg.KEYDOWN:
                if event.key == pg.K_ESCAPE or event.key == pg.K_q:
                self.running = False

    def draw(self):
        self.screen.fill((170, 238, 187))

    def update(self):
        pg.display.flip()
        self.clock.tick(self.FPS)

    def run(self):
        self.running = True
        while self.running:
            self.check_event()
            self.draw()
            self.update()
        pg.quit()
        sys.exit()

Each part of the code above is explained below.

3.2. pygame.init()

Use pygame.init() for convenience, rather than initializing sperate pygame modules.

pygame.init(): Initialize all imported pygame modules

See: https://www.pygame.org/docs/ref/pygame.html#pygame.init

3.3. pygame.display.set_mode

Use pg.display.set_mode to set the window screen size.

pygame.display.set_mode(size=(0, 0), flags=0, depth=0, display=0, vsync=0): Initialize a window or screen for display

Returns a display Surface object.

If no size is passed or is set to (0, 0), the created Surface will have the same size as the current screen resolution.

See: https://www.pygame.org/docs/ref/display.html#pygame.display.set_mode

3.4. pg.display.set_caption()

Use pg.display.set_caption to set the window caption that appears in the top left of the window.

pygame.display.set_caption(title): Change the name on the window.

See: https://www.pygame.org/docs/ref/display.html#pygame.display.set_caption

3.5. pg.time.Clock()

Use pg.time.Clock() to set create a Clock object to control the game framerate.

pygame.time.Clock(): Creates a new Clock object that can be used to track an amount of time.

The clock also provides several functions to help control a game’s framerate.

See: https://www.pygame.org/docs/ref/time.html#pygame.time.Clock

3.6. clock.tick()

After using pg.time.Clock() to set create a Clock object called clock, delay the game.

clock.tick(framerate=0): Call if once per game loop (frame).

If no argument is passed, it returns the milliseconds since the last call

If a framerate argument is passed, it will delay to keep the game running slower than the given ticks per second.

By calling Clock.tick(60) once per frame, the program will never run at more than 60 frames per second.

See: https://www.pygame.org/docs/ref/time.html#pygame.time.Clock.tick

3.7. check_event

check_event has starter code to make sure that exiting the game works well.

The game can be exited by clicking the window close box or by pressing the q or escape buttons.

3.8. pg.event.get()

Use pg.event.get() to get the events for checking using actions.

pygame.event.get(): get all the messages and remove them from the queue.

See: https://www.pygame.org/docs/ref/event.html#pygame.event.get

3.9. event.type and event.key

event.type == pg.QUIT responds to closing the window by clicking on the X button in the top right.
event.type == pg.KEYDOWN responds to key presses.
event.key == pg.K_ESCAPE is True if the escape key is pressed.
event.key == pg.K_q is True if the “q” key is pressed.

For lists of various event types see: https://www.pygame.org/docs/ref/event.html#pygame.event.get

3.10. pg.quit()

Use pg.quit() before exiting the program with sys.exit().

pygame.quit(): Uninitialize all pygame modules that have previously been initialized.

When the Python interpreter shuts down, this method is called regardless,

so the program should not need it, except to terminate the pygame resources and continue. | It will not exit the program.

See: https://www.pygame.org/docs/ref/pygame.html#pygame.quit

3.11. sys.exit()

Use sys.exit() to exit the python program.

sys.exit(): Exit the program. Exit from python.

See: https://docs.python.org/2/library/sys.html#sys.exit

3.12. update definition

update has starter code to update the screen and update the clock.

3.13. pg.display.flip()

pygame.display.flip(): Update the full display Surface to the screen

See: https://www.pygame.org/docs/ref/display.html#pygame.display.flip

3.14. draw definition

draw has starter code to draw to the screen.

3.15. screen.fill()

fill(color, rect=None, special_flags=0): Fill the Surface with a solid color.

If no rect argument is given the entire Surface will be filled.

The rect argument will limit the fill to a specific area.

The color argument can be either a RGB sequence, a RGBA sequence or a mapped color index.

If using RGBA, the Alpha (A part of RGBA) is ignored unless the surface uses per pixel alpha (Surface has the SRCALPHA flag).

See: https://www.pygame.org/docs/ref/surface.html?highlight=fill#pygame.Surface.fill