YOU LEARN HERE...

how you can influence the program flow by pressing keyboard keys. Similar to the mouse events, you define in a callback function what should happen when a keyboard key is pressed. The callback function is not called by the program, but automatically by the system when a key is pressed.

EXAMPLES

Example 1: The Turtle draws a kick when any key is pressed

You define a callback function onKeyPressed(key) . This returns the name of the key pressed and calls thel step() function, which draws a step. The callback function is registered via a parameter of makeTurtle(). This tells the system that it should call this function with every keyboard click.

Program: [► WebTigerPython]

from gturtle import *

def onKeyPressed(key):
    print(key)
    step()

def step():
    forward(20)
    right(90)
    forward(20)
    left(90)
    
makeTurtle(keyPressed = onKeyPressed)
addStatusBar(20)
setStatusText("Press any key!")

Example 2: The Turtle is controlled with cursor keys. The callback function onKeyPressed(key) onKeyPressed(key) returns the name of the pressed key. In an if-elif structure, you specify the direction of movement of the turtle. If one of the arrow keys is pressed, the Turtle changes direction and then moves a short distance forwards. To make the movement faster, select speed(-1).

Program: [► WebTigerPython]

from gturtle import *

def onKeyPressed(key):
    if key == "ArrowLeft":
        setHeading(-90)
    elif key == "ArrowRight":
        setHeading(90)
    elif key == "ArrowUp":
        setHeading(0)
    elif key == "ArrowDown":
        setHeading(180)
    forward(10)

makeTurtle(keyPressed = onKeyPressed)
speed(-1)
addStatusBar(20)
setStatusText("Use cursor keys to move me!")

REMEMBER...

is not called by your program, but by the system when you have pressed a key. You can display the name of the keys, in particular the special keys, in the output window with print(key).

The callback function is registered as a parameter of makeTurtle().

TO SOLVE BY YOURSELF