Hi, folks, Some of you may remember that I am teaching some high school students how to program. Because they all love graphics, I have been investigating the turtle module, which I gather is built on top of Tk. I can see that real-time applications are possible. I'm writing a classic "bouncing-balls" program to demonstrate to my students.
In the main program code, I instantiate a turtle.Screen, named sc. I draw a bounding box, whose size is described by the variables edgew and edgeh. I have a list of Turtle objects, which I named balls. I have a timer interval stored in tick. In the main loop of my program, I bind a function to update the positions of the balls to a timer, thus: sc.ontimer(move_balls, tick) Inside my move_balls function, I could not get ANYTHING done without the following declaration: global balls, edgew, edgeh, tick For a while, I had a "quit" function that I bound to the q key: sc.onkeypress(quit, "q") The quit function simply printed a message, and then called sc.bye(). As with move_balls, quit wouldn't work unless I had a "global sc" declaration in it. (My shortened program skips my function and just binds sc.bye to the q key, avoiding the need for globals.) Once I use globals, everything works fine. However, I haven't taught my students a thing about the globals declaration. Furthermore, I was always taught that the need for global variables generally indicated that YOU were writing a SLOPPY program! However, neither Screen.ontimer() not Screen.onkeypress() appear to give me a way to pass arguments to functions of my own. Why don't they? Is this some limitation of Tk? I have worked with other GUI's before, and I don't remember having to jump through this particular hoop. I'm torn between proceeding with turtle, burdening my students with comprehending globals (they're young, they just barely grasp the idea of namespaces) -- or, abandoning turtle for another approach. Comments appreciated! -- https://mail.python.org/mailman/listinfo/python-list
