Teach Your Kids To Code: A Parent-friendly Guide to Python Programming

214 Chapter 9

Putting It all together

The last step is to end the program with pygame.quit() as usual.

Here’s the full program.

DragDots.py

import pygame # Setup

pygame.init()

screen = pygame.display.set_mode([800,600])

pygame.display.set_caption("Click and drag to draw")

keep_going = True

YELLOW = (255,255,0) # RGB color triplet for YELLOW

radius = 15

mousedown = False

while keep_going: # Game loop

for event in pygame.event.get(): # Handling events

if event.type == pygame.QUIT:

keep_going = False

if event.type == pygame.MOUSEBUTTONDOWN:

mousedown = True

if event.type == pygame.MOUSEBUTTONUP:

mousedown = False

if mousedown: # Draw/update graphics

spot = pygame.mouse.get_pos()

pygame.draw.circle(screen, YELLOW, spot, radius)

pygame.display.update() # Update display

pygame.quit() # Exit

The DragDots.py app is so fast and responsive that it almost

feels like we’re painting with a continuous brush instead of a series

of dots; we have to drag the mouse pretty quickly to see the dots

drawn separately. Pygame allows us to build much faster and more

fluid games and animation than the turtle graphics we drew in

previous chapters.

Even though the for loop handles every event during every

pass through the while loop that keeps our app open, Pygame

is efficient enough to do this dozens or even hundreds of times

per second. This gives the illusion of instantaneous motion and

reaction to our every movement and command—an important

consideration as we build animations and interactive games.

Pygame is up to the challenge and is the right toolkit for our

graphics-intensive needs.