Spider Web in Python Turtle

Intermediate · Nature · 63 lines · draws in about 7 seconds

Twelve straight spokes come out from the centre, and a spiral thread hops from spoke to spoke, a little further out each time.

Spider Web in Python Turtle: the finished drawing

import turtle

import math

screen = turtle.Screen()

screen.bgcolor("lightsteelblue")

screen.title("Spider web")

t = turtle.Turtle()

t.speed(9)

t.pensize(2)

t.pencolor("white")

spokes = 12

def draw_leg(heading, bend):

# A leg in two parts with a knee in the middle

t.penup()

t.goto(0, 0)

t.setheading(heading)

t.pendown()

t.forward(30)

t.right(bend)

t.forward(34)

# The spokes: straight threads from the centre outwards

for i in range(spokes):

t.penup()

t.goto(0, 0)

t.setheading(i * 360 / spokes)

t.pendown()

t.forward(215)

# The spiral: hop from spoke to spoke, a little further out each time

t.penup()

for step in range(spokes * 8):

angle = math.radians(step * 360 / spokes)

radius = 15 + step * 2

t.goto(radius * math.cos(angle), radius * math.sin(angle))

t.pendown()

# The spider sits in the middle of its web: four legs on each side

t.pensize(4)

t.pencolor("black")

for heading in [75, 40, 5, -30]:

draw_leg(heading, 50)

for heading in [105, 140, 175, 210]:

draw_leg(heading, -50)

# Its body, head and two white eyes

t.penup()

t.goto(0, -14)

t.dot(46, "black")

t.goto(0, 16)

t.dot(30, "black")

t.goto(-6, 20)

t.dot(8, "white")

t.goto(6, 20)

t.dot(8, "white")

t.hideturtle()

turtle.done()

Open in the editor

How the code works

A leg with a knee

Each leg starts at the centre, walks 30 steps, turns at the knee and walks 34 more. Legs on the right bend with a positive angle and legs on the left with a negative one, so the two sides mirror each other.

def draw_leg(heading, bend):
    # A leg in two parts with a knee in the middle
    t.penup()
    t.goto(0, 0)
    t.setheading(heading)
    t.pendown()
    t.forward(30)
    t.right(bend)
    t.forward(34)

The spokes

The turtle goes back to the centre for every spoke and turns to i * 360 / spokes degrees, so 12 spokes are 30 degrees apart.

# The spokes: straight threads from the centre outwards
for i in range(spokes):
    t.penup()
    t.goto(0, 0)
    t.setheading(i * 360 / spokes)
    t.pendown()
    t.forward(215)

The spiral thread

Each step aims at the next spoke, 2 further out than the step before. math.cos(angle) and math.sin(angle) turn that angle and radius into the x and y for goto(), and spokes * 8 steps go round the web eight times.

# The spiral: hop from spoke to spoke, a little further out each time
t.penup()
for step in range(spokes * 8):
    angle = math.radians(step * 360 / spokes)
    radius = 15 + step * 2
    t.goto(radius * math.cos(angle), radius * math.sin(angle))
    t.pendown()

The spider

Two loops draw four legs on each side. Dots on top of the legs make the body, the head and two white eyes.

# The spider sits in the middle of its web: four legs on each side
t.pensize(4)
t.pencolor("black")
for heading in [75, 40, 5, -30]:
    draw_leg(heading, 50)
for heading in [105, 140, 175, 210]:
    draw_leg(heading, -50)

Make it yours

Change the code above and press Run. Some ideas:

Change spokes = 12 to spokes = 8 for a web with fewer, wider gaps.
Change step * 2 to step * 1.5 and spokes * 8 to spokes * 11 for a tighter spiral with more rings.
Change screen.bgcolor("lightsteelblue") to screen.bgcolor("midnightblue") for a web at night.

What it uses

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