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

180 Chapter 8

You should see an image like the one in Figure 8-2 when you

run ShowDot.py. Take some time to play around with this dot

program—create a different RGB color triplet, draw the dot in a

different location on the screen, or draw a second dot. You’ll begin

to see the power and ease of drawing graphics with Pygame, and

you’ll have fun along the way.

This first program contains the foundation that we’ll build

on to create more complex graphics, animation, and, eventually,

games.

What’s New in Pygame

Before we dive deeper into the exciting world of Pygame, it’s worth

noting some important differences between Pygame and our old

friend turtle graphics:

•    We have a new coordinate system, as shown in Figure 8-3.

Back in turtle graphics, the origin was at the center of the

screen, and y got larger as we went up the screen. Pygame

uses a more common window-oriented coordinate system (we

see this in many other GUI programming languages, includ-

ing Java, C++, and more). The upper-left corner of a window

in Pygame is the origin, (0, 0). The x-coordinate values still

increase as you move to the right (but there are no negative

x-coordinate values, as they would be off the screen to the

left); y-coordinate values increase as you move down (and nega-

tive y-coordinate values would be off the top of the window).

(0, 0)

y

x

10

20

30

40

50

60

70

10 20 30 40 50 60 70

Figure 8-3: Pygame uses a window-oriented

coordinate system.