Hello, Turtle

turtle is a drawing module that ships with Python, so there's nothing to install. It gives you a cursor (the "turtle") that draws a line wherever it goes. Every shape you'll make today comes down to the same little dance: move forward, turn, repeat.

The Setup Block

Open 1-shapes.py. The setup is already written:

import turtle

screen = turtle.Screen()
screen.setup(800, 800)        # an 800 × 800 pixel canvas

t = turtle.Turtle()           # the cursor, at (0, 0), facing right

# ... your code goes in the TODO section ...

turtle.done()                 # keeps the window open when drawing ends

The canvas coordinate system takes a moment to get used to: (0, 0) is the centre. x increases to the right, y increases upward, so the canvas runs from −400 to +400 in both directions.

The grey # lines are comments. Python skips them entirely; they're notes for whichever human reads the file next. The # TODO lines show you where your code goes.

The Commands

Command	What it does
`t.forward(100)`	Move 100 pixels in the current direction, drawing a line
`t.backward(100)`	Move backwards (no turn)
`t.left(90)` / `t.right(90)`	Turn by 90 degrees
`t.penup()` / `t.pendown()`	Lift / lower the pen — move without/with drawing
`t.goto(x, y)`	Jump straight to a coordinate
`t.color("turquoise")`	Change the pen colour (named colours for now)

Draw a Square

t.forward(100)
t.left(90)
t.forward(100)
t.left(90)
t.forward(100)
t.left(90)
t.forward(100)
t.left(90)

If your "square" comes out as a single line, don't re-read the code top to bottom. Trace the turtle's path with your finger instead, starting from the first line. You'll find the missing left(90) yourself, I promise.

The Magic Angle: 360 ÷ sides

Here's the bit I find genuinely lovely. Every regular polygon, no matter how many sides, is the same two moves: forward, then left(360 / sides), repeated sides times. A triangle turns 360 ÷ 3 = 120° at each corner:

t.penup()
t.goto(150, 0)        # move away so the shapes don't overlap
t.pendown()
t.color("coral")
t.forward(80)
t.left(120)
t.forward(80)
t.left(120)
t.forward(80)
t.left(120)

The penup() → goto() → pendown() sandwich is how you place shapes anywhere on the canvas. Forget the penup() and a stray line drags across the canvas to the new position. If you spot one, ask yourself: was the pen up when I called goto()?

A Logo turtle robot, from the cover of Mindstorms by Seymour Papert

Troubleshooting

Symptom	Fix
Window opens, instantly closes	Add `turtle.done()` at the bottom
Turtle draws partway then disappears off-screen	`forward(1000)` on an 800px canvas does that — smaller numbers, or `t.home()` to recentre
`AttributeError: ... has no attribute 'forward'`	You wrote `Turtle.forward()` with a capital T — call it on your turtle: `t.forward()`
The window hides behind VS Code (macOS)	Click the Python rocket icon in the dock

Stretch Challenges

Hexagon: six sides. What's the turn angle? (360 ÷ 6)
Star: draw a five-pointed star. Hint: the turn is 144°, not 72°. The star skips a corner each step and winds around the centre twice (5 × 144° = 720° = two full turns). Use 72° and you get a plain pentagon.
Initials, pen down: draw your two initials as block letters without ever lifting the pen. Sketch the path on paper first, because dead ends like the crossbar of an "A" need a backtrack.
Nested squares: a square, then a slightly smaller one rotated 20° inside it, and again, and again. What has to change between squares?