Drawing a Stop Sign

By the end of this lesson you'll be able to:

• Use variables to store the color, size, and number of sides of a shape
• Use a for loop to draw any regular polygon without repeating code
• Fill a shape with color using begin_fill() and end_fill()

A stop sign is an octagon — a regular 8-sided polygon. Instead of writing eight forward/right pairs by hand, you'll use a loop and a formula to draw it in just a few lines.

Welcome to This Lesson!

Ready to level up? In this lesson we're going to draw a real stop sign — red fill, white STOP text, and everything. A for loop is going to do all the heavy lifting for us. Let's code it together!

Using Variables for Shape Properties

When you store the size and color in variables, changing the whole drawing is as easy as editing one line. A variable is a named box that holds a value — give it a descriptive name so the code is easy to read.

distance = 50   # length of each side
sides = 8       # number of sides (8 = octagon)
my_color = "red"

The turn angle for any regular polygon follows a simple formula: divide 360 by the number of sides. For an octagon: 360 ÷ 8 = 45 degrees.

Scratch Bridge

In Scratch you used variables in the Variables drawer — set [distance] to 50. In Python, distance = 50 does exactly the same thing: it creates a variable named distance and stores the value 50 in it.

Filling a Shape with Color

Two commands work as a pair to paint the inside of any shape:

• begin_fill() — tells the turtle "start remembering the path"
• end_fill() — tells the turtle "now fill in everything inside that path"

Everything drawn between those two calls gets filled with the current color. If you forget either one, the fill won't appear.

Sample Code

import turtle
monty = turtle.Turtle()
monty.shape('turtle')

distance = 50
sides = 8
angle = 360 / sides  # works for any regular polygon
my_color = "red"

monty.penup()
monty.goto(-50, 100)
monty.pendown()
monty.color(my_color)
monty.begin_fill()

for i in range(sides):
    monty.forward(distance)
    monty.right(angle)

monty.end_fill()
monty.hideturtle()

monty.penup()
monty.right(110)
monty.forward(80)
monty.color('white')
monty.write('STOP', font=("Arial", 30, "normal"))

What Do You Think Will Happen?

Look at the line for i in range(sides): — and remember that sides = 8. How many times will the loop repeat? And what color will the inside of the shape be? Make your guesses — then click Run!

Try It Now

Edit the code below and click Run to draw the stop sign right on this page. No account needed — everything runs in your browser.

▶ Run ↻ Reset

Were you right? The loop runs 8 times (once for each side of the octagon) and the inside fills with red because my_color = "red" was set before begin_fill().

How It Works

The turn angle formula 360 / sides is the secret: the exterior angles of any regular polygon always add up to exactly 360 degrees. Divide by the number of sides and you get the angle for one corner.

goto(-50, 100) moves the turtle to a starting corner without drawing — penup() lifts the pen first so no line appears. pendown() lowers it again before drawing begins.

hideturtle() removes the turtle icon when drawing is finished so it doesn't cover the artwork.

write('STOP', font=...) places text at the turtle's current position using the specified font family, size, and style.

Explanation Table

Line	What it does
distance = 50	Length of each side in pixels
sides = 8	Number of sides — change this to get a different polygon
angle = 360 / sides	Turn angle — the formula works for any regular polygon
my_color = "red"	Stores the color in a variable so it's easy to change
penup() / goto() / pendown()	Move to start position without drawing a line
begin_fill() / end_fill()	Fill everything drawn between them with the current color
for i in range(sides):	Repeat the loop body once for each side
hideturtle()	Hides the turtle cursor when drawing is done
write('STOP', font=...)	Writes text at the turtle's current position

Learning Check

Spot the Bug!

The program below should draw a filled red octagon, but when you run it the shape has no fill — just an outline. One line is in the wrong place. Can you find it and fix it?

▶ Run ↻ Reset

Experiments

Try these changes to the stop sign code above. Predict what will happen first, then run it!

1. Change my_color = "red" to "blue". You'll know it worked when the octagon fills with blue instead of red.

2. Change distance = 50 to 80. You'll know it worked when the stop sign is noticeably larger.

3. Change sides = 8 to 6 — and also update angle = 360 / sides stays the same (it recalculates automatically). You'll know it worked when you see a filled hexagon instead of an octagon.

4. Change 'STOP' to your own word. You'll know it worked when your word appears on the sign in white.

5. Change monty.color('white') (the text color) to 'yellow'. You'll know it worked when the text on the sign turns yellow. Can you still read it easily?

Great Work!

You drew a stop sign using variables, a loop, and fill commands — that's serious Python! Try changing sides to 3 or 5 and see what signs you can invent. Let's code it together!