Drawing a Square

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

• Move the turtle forward and turn it using forward() and right()
• Explain what the numbers inside forward(100) and right(90) control
• Draw a square by repeating the same two commands four times

The turtle starts in the center of the canvas and draws lines as it moves — like a pen attached to a robot. In this lesson you'll give it your first drawing commands and watch a square appear.

Welcome to This Lesson!

Hi, I'm Monty! I'm a Python snake, and today I'm going to teach you how to make me draw a square on the screen. It's easier than you think — let's code it together!

Moving and Turning

The two most important turtle commands are forward() and right().

forward(100) tells the turtle to walk forward 100 steps, drawing a line as it goes. The number inside the parentheses is called a parameter — it controls how much the command does. Here, 100 sets how long each side of the square will be.

right(90) tells the turtle to turn right 90 degrees without drawing anything. The number 90 is a quarter-turn — exactly the angle at each corner of a square.

Scratch Bridge

In Scratch you used the "Move 10 steps" block and the "Turn ↻ 15 degrees" block. In Python, forward(100) and right(90) do exactly the same things — just written differently!

Sample Code

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

monty.forward(100)
monty.right(90)

monty.forward(100)
monty.right(90)

monty.forward(100)
monty.right(90)

monty.forward(100)
monty.right(90)

What Do You Think Will Happen?

Before you click Run, count the forward commands in the code above. How many sides will the turtle draw? Make your guess — then find out!

Try It Now

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

▶ Run ↻ Reset

Were you right? The turtle draws 4 sides — one for each forward() + right() pair — making a perfect square.

If you see a red error message: Check your spelling — Python is case-sensitive, so Forward(100) won't work but forward(100) will. Make sure you have parentheses () around every number.

How It Works

The turtle starts in the center of the canvas facing right. Each forward(100) moves it 100 steps in the direction it is currently facing. Each right(90) rotates it 90 degrees clockwise — a quarter turn. After four forward-and-turn pairs the turtle is back where it started: a perfect square.

Explanation Table

Line	What it does
import turtle	Loads the turtle graphics library
monty = turtle.Turtle()	Creates a turtle and names it monty
monty.shape('turtle')	Shows the turtle icon instead of a plain arrow
monty.forward(100)	Moves 100 steps forward, drawing a line
monty.right(90)	Turns 90 degrees clockwise (one corner of a square)

Common Mistake: Wrong Turn Angle

If you change right(90) to right(100) the corners won't close and you won't get a square! A square needs exactly 90-degree turns. Try it and see what shape you get instead.

Learning Check

Your Turn — Complete the Triangle

A triangle has 3 sides. Each corner of an equilateral triangle turns 120 degrees. The program below is missing one line. Add it so Monty draws a complete triangle!

▶ Run ↻ Reset

Experiments

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

1. Change 100 to 150 in all four forward calls. You'll know it worked when the square is noticeably larger than before.

2. Change all four right(90) calls to right(120) and remove one forward/right pair (leaving only three). You'll know it worked when you see a triangle instead of a square.

3. Add monty.color('red') on the line just before the first forward. You'll know it worked when all four sides of the square are red instead of black.

4. Add monty.speed(1) after monty.shape('turtle') to slow Monty way down. You'll know it worked when you can watch him draw each side one at a time.

5. Try drawing two squares side by side: after the four pairs, add monty.penup(), then monty.forward(150), then monty.pendown(), then repeat the four forward/right pairs again. You'll know it worked when you see two separate squares on the canvas.

Great Work!

You just wrote your first turtle drawing program — and it works! In the next lesson you'll learn how to use a for loop so you don't have to repeat those four lines over and over. Let's code it together!