Turtle Graphics: Where code comes to life. Control the turtle, draw shapes, and master loops!

Moving

Driving instructions.

  • forward(100) Move forward 100 steps.
    Shortcut: fd(100)
  • backward(50) Move back 50 steps.
    Shortcut: bk(50)
  • left(90) Turn left 90 degrees.
    Shortcut: lt(90)
  • right(45) Turn right 45 degrees.
    Shortcut: rt(45)

Pen & Looks

Pen Control
penup() # Don't draw
goto(50, 100) # Teleport
pendown() # Draw again
Styling
pensize(5) # Thickness
color("red") # Line color
speed(5) # 1=slow, 10=fast
Shapes
circle(50) # Radius 50
dot(20) # Filled dot

Loops & Angles

Don't repeat yourself! Use a for loop.

Drawing a Square
for i in range(4):
  forward(100)
  right(90)
Which Angle? TURN Inside

Turtle turns the RED angle (External).

The Angle Formula:
360 / Sides = Angle Triangle: 360 / 3 = 120
Pentagon: 360 / 5 = 72

Functions

Level Up

Teach the turtle a new word (command).

1. Define It
def draw_square():
  for i in range(4):
    forward(50)
    right(90)
2. Call It
draw_square() # Draws one
penup()
forward(100)
pendown()
draw_square() # Draws another

Filling

Colour inside the lines.

color("black", "yellow")
# (Line Colour, Fill Colour)

begin_fill() # Start

for i in range(4):
  forward(100)
  right(90)

end_fill() # Finish
You must close the shape for the fill to look right!

Turtle Debugging

  • Where am I facing?

    Before moving, check your direction.
    Use setheading(0) to face East (Right) if lost.

  • Turtle won't move?

    Check your spelling! foward vs forward.

  • Weird Shape?

    Use External Angles (the turn), not the angle inside.
    Triangle turn is 120 (not 60).

  • No Line Appearing?

    Did you use penup()? Remember to pendown() to start drawing again.

  • Window closes instantly?

    Add done() at the very end of your file.

Dashed Line

Pen Up/Down practice.

for i in range(10):
  forward(10) # Draw
  penup()
  forward(10) # Skip
  pendown()

Staircase

Alternating turns.

for i in range(5):
  forward(30)
  left(90)
  forward(30)
  right(90)

Gold Star

Sharp angles.

color("gold")
begin_fill()
for i in range(5):
  forward(100)
  right(144)
end_fill()

Tip: Experiment! Change numbers and see what happens.