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Event Handling Code (basic)

  1. Oct 31, 2015 #1
    Hi,

    I'm trying to take keyboard inputs to make changes to a turtle from the 'Turtle' graphics in Python.

    I'm not able to register keyboard inputs for the code I've written. I've tested out the examples that had been provided online, and they seem to work fine. I'm not quite sure where I'm going wrong.

    Please have a look at the code and let me know your thoughts:

    Code (Text):

    import turtle

    t = turtle.Turtle()

    turtle.setup(1200,720)

    t.pensize(3)
    t.color("red")
    t.speed(3)
    t.shape()

    colour = ["red","green","blue"]        #turtle can be of three colours

    wn = turtle.Screen()
    wn.title("Turtle Lives!")


    def change_colour(t,k):                #change colour of turtle according to array
        t.color(colour[k])

    pen_size = 3

    def change_size(t,k):                #increase / decrease turtle pen_size
        global pen_size                    #modifying global pen_size variable
        if pen_size > 0:
            if k==1:
                pen_size +=1
            elif k==0:
                pen_size -=1
        t.pensize(pen_size)


    wn.onkey(change_colour(t,0),"r")    #Change colour
    wn.onkey(change_colour(t,1),"g")
    wn.onkey(change_colour(t,2),"b")

    wn.onkey(change_size(t,1),"+")        #Increase / Decrease size
    wn.onkey(change_size(t,0),"-")

    wn.listen()
    wn.mainloop()

     
     
  2. jcsd
  3. Oct 31, 2015 #2
    Hi,

    I've identified the bug: the onkey() function isnt passing arguments through to the code.

    I.e.
    Code (Text):

    wn.onkey(change_size(t,1) ,"+")

    #has to be altered to

    change_size(change_size,"+")
     
    How can I pass these arguments through the keyboard inputs?[/code]
     
  4. Oct 31, 2015 #3

    Mark44

    Staff: Mentor

    According to the Python 3.4.2 documentation that I have, the onkey() event handler (I think this is the right terminology) takes two arguments. The first is the name of a function, with no arguments, and the second is the key you're interested in.
     
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