Python Turtle Graphics

What is Turtle Graphics?

Turtle graphics is a beginner-friendly way to learn programming concepts visually: you control an on-screen turtle with drawing commands, and its trail traces out shapes as it moves.

It requires an actual graphical display to run -- browser-based environments like Pyodide can render it directly in a web page.

Example: What is Turtle Graphics?

import turtle
t = turtle.Turtle()  # the on-screen turtle that draws as it moves
print(type(t))

Moving the Turtle

The turtle is moved with forward() and backward() to travel in the direction it's currently facing, and left()/right() to rotate it by a given number of degrees before its next forward movement -- this relative movement model (not absolute x/y coordinates) is what makes turtle graphics intuitive for drawing shapes.

Example: Moving the Turtle

import turtle
t = turtle.Turtle()
t.forward(100)  # moves in the direction it's currently facing
t.left(90)  # rotates 90 degrees before the next move
t.forward(50)

Drawing Basic Shapes

Repeating a short sequence of forward-and-turn commands inside a loop is how you draw regular shapes: a square is four repetitions of 'move forward, turn 90 degrees,' and any regular polygon follows the same pattern with a different turn angle and repeat count.

Example: Drawing Basic Shapes

import turtle
t = turtle.Turtle()
for _ in range(4):  # four repetitions traces out a square
    t.forward(100)
    t.left(90)

Customizing Colors and Pens

color() sets the pen's drawing color, pensize() sets how thick the drawn line is, and speed() controls how fast the turtle animates its movement -- purely cosmetic controls that don't affect the shape being drawn, only how it looks and how quickly it appears.

Example: Customizing Colors and Pens

import turtle
t = turtle.Turtle()
t.color("blue")  # sets the pen's drawing color
t.pensize(3)  # sets the line thickness
t.speed(1)  # controls animation speed, purely cosmetic
t.forward(100)

Filling Shapes with Color

begin_fill() starts recording the outline of a shape for filling, and end_fill() closes that outline and fills the enclosed area with the current color.

Forgetting to call end_fill() after begin_fill() leaves the shape outlined but unfilled, since the fill only actually renders once the pair is complete.

Example: Filling Shapes with Color

import turtle
t = turtle.Turtle()
t.color("red")
t.begin_fill()  # starts recording the outline to fill
for _ in range(4):
    t.forward(100)
    t.left(90)
t.end_fill()  # closes the outline and fills it with the current color