Square Spiral in Python Turtle

Beginner · Patterns and spirals · 20 lines · draws in about 9 seconds

Each line is 4 steps longer than the one before and the turtle turns 90 degrees after every line, so the path winds outward in a square spiral.

Square Spiral in Python Turtle: the finished drawing

import turtle

screen = turtle.Screen()

screen.bgcolor("black")

screen.title("Square spiral")

t = turtle.Turtle()

t.speed(10)

t.pensize(3)

colors = ["red", "gold", "lime", "deepskyblue"]

# Each line is a little longer than the one before, with a right angle between

for i in range(1, 100):

t.pencolor(colors[i % 4])

t.forward(i * 4)

t.right(90)

t.hideturtle()

turtle.done()

Open in the editor

How the code works

Four colours in a list

The list holds the four pen colours, one for each side of a square. That is why each side of the spiral keeps its own colour all the way out.

colors = ["red", "gold", "lime", "deepskyblue"]

A line that grows every time

i counts from 1 to 99, so forward(i * 4) draws lines of 4, 8, 12 steps and so on. colors[i % 4] picks the next colour and goes back to the first after the fourth, and right(90) makes the corner.

# Each line is a little longer than the one before, with a right angle between
for i in range(1, 100):
    t.pencolor(colors[i % 4])
    t.forward(i * 4)
    t.right(90)

Make it yours

Change the code above and press Run. Some ideas:

Change t.right(90) to t.right(91) and the spiral twists as it grows.
Change i * 4 to i * 2 for a smaller spiral with the lines packed closer together.
Add "violet" to the list and change i % 4 to i % 5 so the colours wind around the spiral instead of keeping to one side each.

What it uses

Every turtle command the site supports is listed on Python turtle online.