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

170 Chapter 7

This function takes the parameters x and y for the location to

start drawing each spiral, and the parameter size to tell us how

big to make the spiral. Inside the function, we lift the turtle’s pen

so that we can move without leaving a trail, we move the pen to

the given (x, y) location, and we put the pen back down to prepare

for the spiral. Our for loop will iterate m over the values from 0 to

size, drawing a square spiral up to that side length.

All we’ll have to do in our program, besides importing random

and turtle and setting up our screen and list of colors, is tell the

computer to listen for clicks on the turtle screen and call the draw_

kaleido() function whenever a click event happens. We can do that

with the command turtle.onscreenclick(draw_kaleido).

Putting It All Together

Here’s the full ClickKaleidoscope.py program. Type it in IDLE or

download it from http://www.nostarch.com/teachkids/ and run it.

ClickKaleidoscope.py

import random

import turtle

t = turtle.Pen()

t.speed(0)

t.hideturtle()

turtle.bgcolor("black")

colors = ["red", "yellow", "blue", "green", "orange", "purple",

"white", "gray"]

def draw_kaleido(x,y):

t.pencolor(random.choice(colors))

size = random.randint(10,40)

draw_spiral(x,y, size)

draw_spiral(-x,y, size)

draw_spiral(-x,-y, size)

draw_spiral(x,-y, size)

def draw_spiral(x,y, size):

t.penup()

t.setpos(x,y)

t.pendown()

for m in range(size):

t.forward(m*2)

t.left(92)

turtle.onscreenclick(draw_kaleido)

We begin with our normal import statements and then set

up our turtle environment and list of colors. Next, we define our