Python Turtle - Graphics Keyboard Commands

Python Turtle module is a graphical tool that can be used to draw simple graphics on the screen using a cursor. Python Turtle was a part of Logo programming language which had similar purpose of letting the users draw graphics on the screen with the help of simple commands. Turtle is a pre-installed module and has inbuilt commands and features that can be used to draw pictures on the screen. This article will be primarily focused on creating a graphic using keyboard commands along with how the same methodology can be used to add or change color to the graphic.

Functions Used:

• Screen() - used to create a canvas for drawing
• Turtle Motion:
  • forward(distance) | fd(distance) : move the turtle forward
  • backward(distance) | back(distance) | bk(distance) : move the turtle backwards
  • right(distance) | rt(distance) : move the turtle right
  • left(distance) | lt(distance) : move the turtle left
  • circle(radius) : draws a circle with a given radius
• Coloring:
  • color() : set the colors
  • begin_fill() : this method is called before drawing a shape that is to be filled
  • end_fill() : Fills the shape drawn after the call to begin_fill().

Given below are two approaches that deal and discuss how to create a graphics keyboard

Method 1

Approach

• Import module and submodules
• Create setup- The setup() method sets up a window of size 500x500.
• Create window- The Screen() method creates a canvas for drawing.
• Instantiate turtle object
• Set turtle speed to 0 which is maximum
• Set visibility- The showturtle() method sets the visibility of the turtle.
• In order to capture the keystrokes we need to define few functions namely up, down, left, right. By default, the turtle points to the right.
  • The setheading() method changes the orientation of the turtle to the given angle.
  • The forward() method moves the turtle to the specified distance.
  • The listen() method sets focus on the turtle screen to capture events.
  • The onkey() method invokes the method specific to the captured keystroke. The first argument of onkey() is the function to be called and the second argument is the key.
  • The Up,Down,Left and Right are the corresponding arrow keys on the keyboard.
• Add mainloop() command, it prevents the application from terminating before the user actually clicks the exit option.

Program

import turtle
from turtle import *

setup(500, 500)
Screen()
turtle = turtle.Turtle()
turtle.speed(0)
showturtle()


def up():
    turtle.setheading(90)
    turtle.forward(100)


def down():
    turtle.setheading(270)
    turtle.forward(100)


def left():
    turtle.setheading(180)
    turtle.forward(100)


def right():
    turtle.setheading(0)
    turtle.forward(100)


listen()
onkey(up, 'Up')
onkey(down, 'Down')
onkey(left, 'Left')
onkey(right, 'Right')

mainloop()

Output

Method 2: changing color

This is similar to the previous example with the addition of few more keys. Now we have added keys to change the color of the line. 

• If the user presses r it turns red,
• If g it turns green and if b it turns blue.
• For resetting the line color to black the user must press z.

Also, the thickness of the line is increased by setting the width o the turtle to 5px using the width() method.

Program

import turtle
from turtle import *

setup(500, 500)
Screen()
turtle = turtle.Turtle()
turtle.speed(0)
turtle.width(5)
showturtle()


def up():
    turtle.setheading(90)
    turtle.forward(100)


def down():
    turtle.setheading(270)
    turtle.forward(100)


def left():
    turtle.setheading(180)
    turtle.forward(100)


def right():
    turtle.setheading(0)
    turtle.forward(100)


def r():
    turtle.color("red")


def g():
    turtle.color("green")


def b():
    turtle.color("blue")


def z():
    turtle.color("black")


listen()
onkey(up, 'Up')
onkey(down, 'Down')
onkey(left, 'Left')
onkey(right, 'Right')
onkey(z, "z")
onkey(r, 'r')
onkey(g, 'g')
onkey(b, 'b')

mainloop()

Output