Rainbow Spiral

In this activity, we will be creating a “Rainbow Spiral” with the Python programming language and using the Turtle Library.

We will create a program that will draw lines of increasing width around a central point making an attractive pattern.

Taken and adpated from: Geeks for Geeks: Turtle Programming in Python - no4. Rainbow Benzene

1 - Setup

Go to trinkiet.io and start a new Python project: http://bit.ly/pythontrinket (log into your account if you have one or create one to save your progress). Then:

Import the turtle module into your project

import turtle

Initialize Turtle() as t:

t = turtle.Turtle()

Initialize Screen() as s:

s = turtle.Screen()

Set the screen background colour to black:

s.bgcolor('black')

Set turtle speed to fastest:

t.speed('fastest')

2 - The for loop

Write a for loop for a range of 200:

for x in range(200):

Inside the loop (remember it needs to be indented!) set the pen colour:

t.pencolor('blue')

Still inside the loop set the line width to get wider each loop:

t.width(x/100 + 1)

Still inside the loop move the turtle forward to draw a line:

t.forward(x)

Finally, still in the loop, lets change the angle of the turtle to create the spiral:

t.left(79)

3 - Run the program!

You should be able to now run the program. You should get something that looks like this: A blue spiral

4 - Challenges

Can you change the spiral to be a twisty hexagon? (hint: you’ll need to change the angle)
Can you make each stripe in the spiral to be a different colour? (hint: you’ll need to make a list of colours and select from that list)
Can you make the spiral reverse itself and do it continuously? (hint: you’ll need to copy the for loop and reverse something. To make it do it continuously you’ll have to put both for loops inside a while loop)

5 - Challenge Solutions

Twisty hexagon spiral change line 10 to:
```
t.left(59)
```
Different colours for each stripe
- After line 3 insert the following line:
```
colors = ['red', 'purple', 'blue', 'green', 'orange', 'yellow']
```
- On what is now line 8 select from those colours by dividing the current x by 6 and selecting the index with the remainder:
```
t.pencolor(colors[x%6])
```

Reversing, continuous spiral – on line 7 replace the for loop with the following:

while True:
  for x in range(200): 
t.pencolor(colors[x%len(colors)]) 
t.width(x/100 + 1)
t.forward(x) 
t.left(59)
  t.right(239)  
  for x in range(200, 0, -1): 
t.pencolor('black') 
t.width(x/100 + 7)
t.forward(x) 
t.right(59) 